Methods and compositions for diagnosis and prognosis of renal injury and renal failure
阅读说明：本技术 用于诊断和预后肾损伤和肾衰竭的方法和组合物 (Methods and compositions for diagnosis and prognosis of renal injury and renal failure ) 是由 J·安德贝里 P·麦克弗森 J·格雷 K·中村 J·P·坎普夫 T·关 于 2015-10-20 设计创作，主要内容包括：本发明涉及用于诊断和预后肾损伤和肾衰竭的方法和组合物。本发明涉及用于患有或怀疑患有肾损伤的受试者的监测、诊断、预后以及确定治疗方案的方法和组合物。具体地,本发明涉及使用检测作为肾损伤的诊断和预后生物标记物测定的C-C基序趋化因子16、C-C基序趋化因子14和酪氨酸蛋白激酶受体UFO中的一种或多种的测定。(The present invention relates to methods and compositions for the diagnosis and prognosis of renal injury and renal failure. The present invention relates to methods and compositions for monitoring, diagnosis, prognosis, and determining a treatment regimen for a subject having or suspected of having a renal injury. In particular, the invention relates to assays using one or more of C-C motif chemokine 16, C-C motif chemokine 14, and tyrosine protein kinase receptor UFO as a diagnostic and prognostic biomarker assay for renal injury.)
1. A method for evaluating renal status in a subject, comprising:
performing an assay configured to detect C-C motif chemokine 16, an assay configured to detect C-C motif chemokine 14, and/or an assay configured to detect tyrosine protein kinase receptor UFO on a body fluid sample obtained from the subject to provide one or more assay results; and
correlating the assay result with the renal status of the subject.
2. A method according to claim 1, wherein said correlating step comprises correlating the assay result to one or more of risk stratification, diagnosis, staging, prognosis, classifying and monitoring of the renal status of the subject.
3. A method according to claim 1, wherein said correlating step comprises assigning a likelihood of one or more future changes in the renal status of the subject based on the assay result.
4. A method according to claim 3, wherein said one or more future changes in renal status comprise one or more of a future injury to renal function, future reduced renal function, future improvement in renal function, and future Acute Renal Failure (ARF).
5. The method of one of claims 1-4, wherein said assay result comprises a measured concentration of C-C motif chemokine 16, a measured concentration of C-C motif chemokine 14, and/or a measured concentration of tyrosine protein kinase receptor UFO.
6. The method of one of claims 1-5, wherein the correlating step comprises combining the plurality of assay results using a function that converts the plurality of assay results into a single composite result.
7. A method according to claim 3, wherein the one or more future changes in renal status comprise a clinical outcome associated with the renal injury suffered by the subject.
8. A method according to claim 3, wherein said likelihood of one or more future changes in renal status is that an event of interest is more or less likely to occur within 30 days of the time at which the body fluid sample is obtained from the subject.
9. A method according to claim 8, wherein the likelihood of one or more future changes in renal status is that an event of interest is more or less likely to occur within a time period selected from the group consisting of 21 days, 14 days, 7 days, 5 days, 96 hours, 72 hours, 48 hours, 36 hours, 24 hours, and 12 hours.
10. A method according to one of claims 1-5, wherein the subject is selected for evaluation of renal status based on the pre-existence in the subject of one or more known risk factors for prerenal, intrinsic renal, or postrenal ARF.
Background
The following discussion of the background of the invention is provided merely to aid the reader in understanding the invention and is not an admission that the prior art describes or constitutes the present invention.
The kidneys are responsible for the excretion of water and solutes in the body. Its functions include the maintenance of acid-base equilibrium, the regulation of electrolyte concentration, the control of blood volume, and the regulation of blood pressure. Thus, loss of renal function due to injury and/or disease results in a significant amount of morbidity and mortality. A detailed discussion of renal injury is provided in Harrison's Principles of Internal Medicine, 17 th edition, McGraw Hill, New York, pages 1741-1830, which is hereby incorporated by reference in its entirety. The renal disease and/or injury may be acute or chronic. Acute and chronic kidney disease is described below (from Current medical diagnosis & Treatment 2008, 47 th edition, McGraw Hill, New York, pp 785-815, which is hereby incorporated by reference in its entirety): "acute renal failure is a deterioration in renal function over a period of hours to days, resulting in the retention of nitrogenous waste products (such as urea nitrogen) and creatinine in the blood. The retention of these substances is called azotemia. Chronic renal failure (chronic kidney disease) is caused by abnormal loss of renal function for months to years.
Acute renal failure (ARF, also known as acute kidney injury or AKI) is an acute (usually detected within about 48 hours to 1 week) reduction in glomerular filtration. Loss of filtration capacity results in retention of nitrogenous (urea and creatinine) and non-nitrogenous waste normally excreted by the kidney, a reduction in urine excretion, or both. ARF has been reported to complicate about 5% of hospitalizations, 4% -15% of cardiopulmonary bypass surgery, and up to 30% of intensive care. ARF can be classified as prerenal, intrinsic renal, or postrenal, depending on the etiology. Nephrogenic disorders can be further divided into glomerular, tubular, interstitial and vascular abnormalities. The main causes of ARF are described in the following table, adapted from Merck Manual, 17 th edition, chapter 222, and hereby incorporated by reference in its entirety:
in the case of ischemic ARF, the course of the disease can be divided into four stages. During the initial phase, which lasts from hours to days, reduced perfusion of the kidney is evolving into injury. Glomerular ultrafiltration is reduced, the flow of filtrate is reduced by debris in the tubules, and filtrate leaks back through the damaged epithelium. Reperfusion of the kidney may mediate kidney injury during this phase. Initiation is followed by an extension phase characterized by persistent ischemic injury and inflammation, and may involve endothelial injury and vascular congestion. During the maintenance phase, which lasts for 1 to 2 weeks, renal cell injury occurs and glomerular filtration and urine output reach a minimum. This is followed by a recovery phase in which the renal epithelium is repaired and GFR gradually recovers. Nevertheless, survival rates of subjects with ARF can be as low as about 60%.
Acute kidney injury caused by radiocontrast agents (also known as contrast agents) and other nephrotoxins, such as cyclosporine, antibiotics (including aminoglycosides), and anticancer drugs (such as cisplatin), develops over a period of days to about a week. Contrast-induced nephropathy (CIN, AKI caused by radiocontrast agents) is thought to be caused by intrarenal vasoconstriction (leading to ischemic injury) and by the production of reactive oxygen species that are directly toxic to renal tubular epithelial cells. CIN typically shows an acute (onset within 24-48 hours) but reversible (peak 3-5 days, breakdown within 1 week) rise in blood urea nitrogen and serum creatinine.
A commonly reported criterion for defining and detecting AKI is a sudden (typically within about 2-7 days or hospitalization period) increase in serum creatinine. Although the use of serum creatinine elevation to define and detect AKI is well established, the magnitude of serum creatinine elevation and the time at which it is measured to define AKI varies greatly in publications. Traditionally, relatively large increases in serum creatinine such as 100%, 200%, increases of at least 100% to values in excess of 2mg/dL, and other definitions are used to define AKI. However, a recent trend has been towards using smaller elevations in serum creatinine to define AKI. The relationship between serum creatinine elevation, AKI and associated health risks is reviewed in Praught and Shlipak, Curr Opin Nephrol Hypertens 14: 265. sup. 270, 2005 and Chertow et al, J Am Soc Nephrol 16: 3365-3370, 2005, which is hereby incorporated by reference in its entirety with the references listed herein. As described in these publications, it is now known that an increased risk of acute renal function deterioration (AKI) and death and other deleterious consequences is associated with a very small increase in serum creatinine. These increases may be determined as relative (percent) values or nominal values. Relative increases in serum creatinine from pre-injury values as small as 20% have been reported to indicate acute renal function deterioration (AKI) and increased health risk, but more commonly reported values to define AKI and increased health risk are at least 25% relative increases. It has been reported that nominal increases as small as 0.3mg/dL, 0.2mg/dL, or even 0.1mg/dL indicate an increase in renal function deterioration and risk of death. Various periods of serum creatinine rise to these thresholds have been used to define AKI, e.g., 2 days, 3 days, 7 days, or variable periods of time defined as when the patient is in the hospital or intensive care unit. These studies indicate that there is no specific threshold (or period of time of rise) of serum creatinine rise for worsening renal function or AKI, but rather that there is a continuing increase in risk as the magnitude of serum creatinine rise increases.
One study (Lassnigg et al, J Am Soc Nephrol 15:1597-1605, 2004, hereby incorporated by reference in its entirety) investigated the elevation and depression of serum creatinine. Patients with mild decreases in serum creatinine from-0.1 mg/dL to-0.3 mg/dL after cardiac surgery had the lowest mortality rates. Patients with a greater decline (greater than or equal to-0.4 mg/dL) in serum creatinine or any elevated serum creatinine had greater mortality. These findings led the authors to conclude that even very subtle changes in renal function (such as minor changes in creatinine detected within 48 hours of surgery) severely affected the outcome of the patient. In an effort to reach a consensus of a unified classification system using serum creatinine to define AKI in clinical trials and clinical practice, Bellomo et al, Crit care.8(4): R204-12, 2004 (hereby incorporated by reference in its entirety) proposed the following classification method for the classification of AKI patients:
"risk": urine volume at 1.5 fold or 6 hours elevated serum creatinine baseline <0.5ml/kg body weight/hour;
"Damage": serum creatinine elevated to 2.0 fold of baseline or urine volume <0.5 ml/kg/hour at 12 hours;
"exhaustion": serum creatinine elevated to 3.0 fold at baseline or creatinine >355 μmol/l (with an elevation > 44) or a urine output of less than 0.3 ml/kg/hr for 24h, or at least 12 h anuria;
and includes two clinical outcomes:
"loss": renal replacement therapy is required continuously for more than four weeks.
"ESRD": end stage renal disease-dialysis is required for more than 3 months.
These criteria, known as RIFLE criteria, provide a useful clinical tool to classify renal status. As with Kellum, crit. care med.36: as discussed in S141-45, 2008 and Ricci et al, Kidney int.73, 538-546, 2008 (each hereby incorporated by reference in its entirety), the RIFLE standard provides a unified definition of AKI that has been validated in many studies.
More recently, a similar classification method for fractionation of AKI patients, improved from RIFLE, was proposed in meita et al, crit.care 11: R31(doi:10.1186.cc5713), 2007 (which is hereby incorporated by reference in its entirety):
"phase I": serum creatinine increases greater than or equal to 0.3mg/dL (. gtoreq.26.4. mu. mol/L), or to 150% of baseline (1.5-fold) or to a urine output of less than 0.5 mL/kg/hr over 6 hours;
"phase II": serum creatinine rise to 200% (>2 fold) above baseline or urine output of less than 0.5 mL/kg/hr over 12 hours;
"stage III": serum creatinine was elevated to 300% (>3 fold) above baseline, or serum creatinine > 354 μmol/L with an acute elevation of at least 44 μmol/L or 24 hour urine output of less than 0.3 mL/kg/hour or for 12 hours anuria.
The CIN consensus working group (McCollough et al, Rev Cardiovasc Med.2006; 7(4): 177-. Although different populations suggest slightly different criteria for detecting AKI using serum creatinine, it is well recognized that small changes in serum creatinine, such as 0.3mg/dL or 25%, are sufficient to detect AKI (worsening renal function), and that the magnitude of the change in serum creatinine is an indicator of the severity and risk of death of AKI.
While continuous measurement of serum creatinine over periods of several days is accepted as one of the most important tools for the detection and diagnosis of AKI in patients with AKI, it is generally recognized that serum creatinine has several limitations in the diagnosis, assessment and monitoring of AKI patients. The period of time for which serum creatinine rises to a value considered diagnostic for AKI (e.g., 0.3mg/dL or 25% rise) may be 48 hours or more, depending on the definition used. Since cellular damage in AKI can occur over a period of hours, serum creatinine elevation detected at 48 hours or more may be a late indicator of damage, and thus dependence on serum creatinine may delay diagnosis of AKI. Furthermore, when renal function changes rapidly, serum creatinine is not a good indicator of the precise renal status and the need for treatment during the most acute phase of AKI. Some patients with AKI will recover completely, some will require dialysis (short or long term), and some will have other adverse consequences including death, severe adverse cardiac events, and chronic kidney disease. Because serum creatinine is a marker of filtration rate, it does not distinguish the cause of AKI (prerenal, intrinsic renal, postrenal obstruction, atheromatous, etc.) or the type or location of injury in an intrinsic renal disease (e.g., originating from the tubules, glomeruli, or interstitium). Urine output is similarly limited and understanding of these matters is crucial for managing and treating patients with AKI.
These limitations underscore the need for better methods to detect and assess AKI, particularly in the early and subclinical stages, as well as in the late stages where renal recovery and repair may occur. Furthermore, there is a need to better identify patients at risk of suffering from AKI.
Summary of The Invention
It is an object of the present invention to provide methods and compositions for evaluating renal function in a subject. As described herein, measurement of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and tyrosine kinase receptor UFO (collectively referred to herein as "kidney injury markers," and individually as "kidney injury markers") can be used to diagnose, prognose, risk stratification, staging, monitoring, classifying, and determine further diagnosis and treatment regimens in a subject having or at risk of having an injury to renal function, reduced renal function, and/or acute renal failure (also referred to as an acute kidney injury).
These kidney injury markers can be used alone or in combination comprising a plurality of kidney injury markers for risk stratification (i.e., identifying a subject at risk of future renal function injury, future development of reduced renal function, future development of ARF, future improvement in renal function, etc.); for diagnosing existing diseases (i.e., identifying subjects suffering from an injury to renal function, having developed reduced renal function, and having developed ARF, etc.); for monitoring deterioration or improvement of kidney function; and for predicting a future medical outcome, such as an improvement or worsening of kidney function, a reduction or improvement in risk of mortality, a reduction or improvement in risk that the subject will need to undergo renal replacement therapy (i.e., hemodialysis, peritoneal dialysis, hemofiltration, and/or kidney transplantation), a reduction or improvement in risk that the subject will recover from an injury to renal function, a reduction or improvement in risk that the subject will recover from ARF, a reduction or improvement in risk that the subject will develop end-stage renal disease, a reduction or improvement in risk that the subject will develop chronic renal failure, a reduction or improvement in risk that the subject will suffer from rejection of transplanted kidneys, and the like.
In a first aspect, the present invention relates to a method for assessing renal status in a subject. These methods comprise performing an assay configured to detect one or more kidney injury markers of the invention from a bodily fluid sample obtained from a subject. The assay results, e.g., measured concentrations of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine protein kinase receptor UFO, are then correlated with the renal status of the subject. Such correlation with renal status can include correlating the assay result with one or more of risk stratification, diagnosis, prognosis, staging, classifying and monitoring of the subject described herein. Thus, the present invention utilizes one or more kidney injury markers of the present invention to assess kidney injury.
In certain embodiments, the methods of assessing renal status described herein are methods of risk stratification of a subject; that is, assigning a likelihood of one or more future changes in renal status to the subject. In these embodiments, the assay result is correlated with one or more of such future changes. The following are preferred embodiments of risk stratification.
In preferred risk stratification embodiments, the methods comprise determining a subject's risk of a future injury to renal function and correlating the assay result, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, to the likelihood of such future injury to renal function. For example, the measured concentrations may each be compared to a threshold. For a "positive going" kidney injury marker, an increased likelihood of a given subject suffering a future injury to renal function is assigned when the measured concentration is above the threshold, relative to a likelihood assigned when the measured concentration is below the threshold. For a "negative going" kidney injury marker, an increased likelihood is assigned that the subject will suffer a future injury to renal function when the measured concentration is below the threshold, relative to a likelihood assigned when the measured concentration is above the threshold.
In other preferred risk stratification embodiments, the methods comprise determining a subject's risk of future reduced renal function and correlating the assay results, e.g., measured concentrations of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, with the likelihood of such reduced renal function. For example, the measured concentrations may each be compared to a threshold. For a "positive going" kidney injury marker, an increased likelihood of a given subject suffering from reduced renal function in the future is assigned when the measured concentration is above the threshold, relative to a likelihood assigned when the measured concentration is below the threshold. For a "negative going" kidney injury marker, an increased likelihood of a given subject suffering from reduced renal function in the future is assigned when the measured concentration is below the threshold, relative to a likelihood assigned when the measured concentration is above the threshold.
In yet another preferred risk stratification embodiment, the methods comprise determining the likelihood of a future improvement in renal function in the subject and correlating the assay result, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, with such likelihood of future improvement in renal function. For example, the measured concentrations may each be compared to a threshold. For a "positive going" kidney injury marker, an increased likelihood of future improvement in renal function is assigned to the subject when the measured concentration is below the threshold, relative to a likelihood assigned when the measured concentration is above the threshold. For a "negative going" kidney injury marker, an increased likelihood of future improvement in renal function is assigned to the subject when the measured concentration is above the threshold, relative to a likelihood assigned when the measured concentration is below the threshold.
In yet another preferred risk stratification embodiment, the methods comprise determining the subject's risk of progression to ARF and correlating the results, e.g., measured concentrations of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine protein kinase receptor UFO, with this likelihood of progression to ARF. For example, the measured concentrations may each be compared to a threshold. For a "positive going" kidney injury marker, the likelihood of a given subject progressing to ARF increases when the measured concentration is above the threshold, relative to the likelihood given when the measured concentration is below the threshold. For a "negative going" kidney injury marker, an increased likelihood of a given subject progressing to ARF is assigned when the measured concentration is below the threshold, relative to a likelihood assigned when the measured concentration is above the threshold.
And in other preferred risk stratification embodiments, the methods comprise determining the risk of outcome for the subject and correlating the assay outcome, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, with the likelihood of occurrence of a clinical outcome associated with the renal injury from which the subject is suffering. For example, the measured concentrations may each be compared to a threshold. For a "positive going" kidney injury marker, the likelihood of a given subject's one or more of acute kidney injury, progression to worsening stage of AKI, death, need for renal replacement therapy, need for withdrawal of nephrotoxins, end stage renal disease, heart failure, stroke, myocardial infarction, progression to chronic kidney disease, etc., increases when the measured concentration is above a threshold relative to the likelihood assigned when the measured concentration is below the threshold. For a "negative going" kidney injury marker, the likelihood of a given subject's one or more of acute kidney injury, progression to worsening stage of AKI, death, need for renal replacement therapy, need for withdrawal of nephrotoxins, end stage renal disease, heart failure, stroke, myocardial infarction, progression to chronic kidney disease, etc., increases when the measured concentration is below a threshold relative to the likelihood given when the measured concentration is above the threshold.
In such a risk stratification embodiment, preferably, the specified likelihood or risk refers to an event of interest that is more or less likely to occur within 180 days from the time the body fluid sample is obtained from the subject. In particularly preferred embodiments, the specified likelihood or risk is associated with an event of interest occurring within a shorter period of time, such as 18 months, 120 days, 90 days, 60 days, 45 days, 30 days, 21 days, 14 days, 7 days, 5 days, 96 hours, 72 hours, 48 hours, 36 hours, 24 hours, 12 hours or less. The risk of 0 hours since the subject obtained a body fluid sample corresponds to the diagnosis of the current symptoms.
In a preferred risk stratification embodiment, the subject is selected for risk stratification based on the pre-existing one or more known risk factors for prerenal, intrinsic renal, or postrenal ARF in the subject. For example, a subject undergoing or having undergone major vascular surgery, coronary artery bypass, or other cardiac surgery; a subject with pre-existing congestive heart failure, preeclampsia, eclampsia, diabetes mellitus, hypertension, coronary artery disease, proteinuria, renal insufficiency, glomerular filtration below the normal range, cirrhosis of the liver, serum creatinine above the normal range, or sepsis; or subjects exposed to NSAIDs, cyclosporines, tacrolimus, aminoglycosides, foscarnet, ethylene glycol, hemoglobin, myoglobin, ifosfamide, heavy metals, methotrexate, radiopaque contrast agents, or streptozotocin, are preferred subjects for risk monitoring according to the methods described herein. This list is not meant to be limiting. By "pre-existing" in this context is meant that a risk factor is present at the time the body fluid sample is taken from the subject. In particularly preferred embodiments, the subject is selected for risk stratification based on an existing diagnosis of renal function injury, reduced renal function, or ARF.
In other embodiments, the methods of assessing renal status described herein are methods of diagnosing a renal injury in a subject; that is, the subject is assessed for having suffered an injury to renal function, reduced renal function, or ARF. In these embodiments, the assay result is correlated with the presence or absence of a change in renal status. The following are preferred diagnostic embodiments.
In a preferred diagnostic embodiment, these methods comprise diagnosing the presence or absence of an injury to renal function and correlating the result of the assay, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, with the presence or absence of such an injury. For example, each measured concentration may be compared to a threshold value. For a positive going marker, a subject is assigned an increased likelihood of developing an injury to renal function when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold); alternatively, a subject may be assigned an increased likelihood of not experiencing an injury to renal function when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, an increased likelihood of the assigned subject exhibiting an injury to renal function when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold); alternatively, a subject may be assigned an increased likelihood of not experiencing an injury to renal function when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold).
In other preferred diagnostic embodiments, the methods comprise diagnosing the presence or absence of reduced renal function and correlating the assay result, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, with the presence or absence of an injury that causes reduced renal function. For example, each measured concentration may be compared to a threshold value. For a positive going marker, an increased likelihood that the subject is assigned an injury that causes reduced renal function when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold); alternatively, a subject may be assigned an increased likelihood of not developing an injury that causes reduced renal function when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, an increased likelihood that the subject is assigned an injury that causes reduced renal function when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold); alternatively, a subject may be assigned an increased likelihood of not developing an injury that causes reduced renal function when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold).
In yet another preferred diagnostic embodiment, the methods comprise diagnosing the presence or absence of ARF and correlating the assay result, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine protein kinase receptor UFO, with the presence or absence of damage that causes ARF. For example, each measured concentration may be compared to a threshold value. For a positive going marker, a subject is assigned an increased likelihood of developing ARF when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold); alternatively, a subject may be assigned an increased likelihood of not developing ARF when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, a subject is assigned an increased likelihood of developing ARF when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold); alternatively, a subject may be assigned an increased likelihood of not developing ARF when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold).
In other preferred risk stratification embodiments, the methods comprise diagnosing a subject in need of renal replacement therapy and correlating the assay results, e.g., measured concentrations of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine protein kinase receptor UFO, with the need for renal replacement therapy. For example, each measured concentration may be compared to a threshold value. For a positive going marker, an increased likelihood that the given subject will develop an injury that results in need of renal replacement therapy when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold); alternatively, a subject may be assigned an increased likelihood of not developing an injury that would result in need of renal replacement therapy when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, an increased likelihood that the designated subject will develop an injury that results in need of renal replacement therapy when the measured concentration is below the threshold (relative to the likelihood designated when the measured concentration is above the threshold); alternatively, a subject may be assigned an increased likelihood of not developing an injury that would result in need of renal replacement therapy when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold).
In other preferred risk stratification embodiments, the methods comprise diagnosing a subject in need of kidney transplantation and correlating the assay results, e.g., measured concentrations of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, with the need for kidney transplantation. For example, each measured concentration may be compared to a threshold value. For a positive going marker, an increased likelihood that the given subject will develop an injury that will result in a need for renal transplantation when the measured concentration is above the threshold (relative to the likelihood that would be assigned when the measured concentration is below the threshold); alternatively, a subject may be assigned an increased likelihood of not developing an injury that requires kidney transplantation when the measured concentration is below the threshold (relative to the likelihood assigned when the measured concentration is above the threshold). For a negative going marker, an increased likelihood that the given subject will develop an injury that will result in a need for kidney transplantation when the measured concentration is below the threshold (relative to the likelihood that would be assigned when the measured concentration is above the threshold); alternatively, a subject may be assigned an increased likelihood of not developing an injury requiring kidney transplantation when the measured concentration is above the threshold (relative to the likelihood assigned when the measured concentration is below the threshold).
In yet another embodiment, the methods of assessing renal status described herein are methods of monitoring renal injury in a subject; that is, assessing whether renal function is improving or worsening in a subject who has suffered an injury to renal function, reduced renal function, or ARF. In these embodiments, an assay result, e.g., a measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, is correlated with the presence or absence of a change in renal status. The following are preferred monitoring embodiments.
In preferred monitoring embodiments, the methods comprise monitoring the renal status of a subject having an impairment of renal function and correlating the assay result, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, with the presence or absence of a change in renal status in the subject. For example, the measured concentration may be compared to a threshold. For a positive going marker, when the measured concentration is above a threshold, the subject can be assigned a worsening renal function; alternatively, when the measured concentration is below a threshold, the subject may be assigned an improvement in renal function. For a negative going marker, a subject may be assigned a worsening renal function when the measured concentration is below a threshold; alternatively, when the measured concentration is above a threshold, the subject may be assigned an improvement in renal function.
In other preferred monitoring embodiments, the methods comprise monitoring the renal status of a subject having reduced renal function and correlating the assay result, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, with the presence or absence of a change in renal status in the subject. For example, the measured concentration may be compared to a threshold. For a positive going marker, when the measured concentration is above a threshold, the subject can be assigned a worsening renal function; alternatively, when the measured concentration is below a threshold, the subject may be assigned an improvement in renal function. For a negative going marker, a subject may be assigned a worsening renal function when the measured concentration is below a threshold; alternatively, when the measured concentration is above a threshold, the subject may be assigned an improvement in renal function.
In yet another preferred monitoring embodiment, the methods comprise monitoring the renal status of a subject having acute renal failure and correlating the assay result, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, with the presence or absence of a change in renal status in the subject. For example, the measured concentration may be compared to a threshold. For a positive going marker, when the measured concentration is above a threshold, the subject can be assigned a worsening renal function; alternatively, when the measured concentration is below a threshold, the subject may be assigned an improvement in renal function. For a negative going marker, a subject may be assigned a worsening renal function when the measured concentration is below a threshold; alternatively, when the measured concentration is above a threshold, the subject may be assigned an improvement in renal function.
In other additional preferred monitoring embodiments, the methods comprise monitoring the renal status of a subject at risk of injury to renal function as a result of a pre-existing one or more known risk factors for prerenal, intrinsic renal, or postrenal ARF, and correlating the assay result, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine protein kinase receptor UFO, with the presence or absence of a change in renal status in the subject. For example, the measured concentration may be compared to a threshold. For a positive going marker, when the measured concentration is above a threshold, the subject can be assigned a worsening renal function; alternatively, when the measured concentration is below a threshold, the subject may be assigned an improvement in renal function. For a negative going marker, a subject may be assigned a worsening renal function when the measured concentration is below a threshold; alternatively, when the measured concentration is above a threshold, the subject may be assigned an improvement in renal function.
In yet another preferred monitoring embodiment, the methods comprise monitoring renal status in a subject having or at risk of a future sustained renal function injury from an acute renal injury. As used herein, "future persistence" refers to an existing acute kidney injury that will continue for a period of time selected from the group consisting of 21 days, 14 days, 7 days, 5 days, 96 hours, 72 hours, 48 hours, 36 hours, 24 hours, and 12 hours. In certain embodiments, the subject has acute kidney injury at the time the sample is obtained. This is not meant to imply that the subject must suffer from an acute kidney injury at the time the sample is obtained, but rather that at the onset of the acute kidney injury, the subject suffers from an acute kidney injury that will persist. In various embodiments, an assay result, e.g., a measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine-protein kinase receptor UFO, is correlated with future persistent acute kidney injury in the subject. For example, the measured concentration may be compared to a threshold. For a positive going marker, when the measured concentration is above a threshold, the subject may be assigned a future persistence of acute kidney injury; alternatively, when the measured concentration is below the threshold, the subject may be assigned a future improvement in renal function. For a negative going marker, when the measured concentration is below the threshold, the subject may be assigned a future persistence of acute kidney injury; alternatively, when the measured concentration is above a threshold, the subject may be assigned a future improvement in renal function.
In yet another embodiment, the methods for evaluating renal status described herein are methods for classifying a renal injury in a subject; that is, determining whether the renal injury in the subject is prerenal, renogenic, or postrenal; and/or further sub-classifying these classes into sub-classes, such as acute tubular injury, acute glomerulonephritis, acute tubulointerstitial nephritis, acute vascular nephropathy, or invasive disease; and/or assigning a likelihood that the subject will progress to a particular RIFLE stage. In these embodiments, an assay result, e.g., a measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine protein kinase receptor UFO, is associated with a particular class and/or subclass. The following are preferred classification embodiments.
In preferred classification embodiments, the methods comprise determining whether the renal injury in the subject is prerenal, renogenic, or postrenal; and/or further subdividing these into sub-classes, such as acute tubular injury, acute glomerulonephritis, acute tubulointerstitial nephritis, acute vascular nephropathy, or invasive disease; and/or assigning a likelihood that the subject will progress to a particular RIFLE stage, and correlating the assay result, e.g., the measured concentration of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and/or tyrosine protein kinase receptor UFO, with the injury classification of the subject. For example, the measured concentration may be compared to a threshold and a specific classification may be assigned when the measured concentration is above the threshold; alternatively, when the measured concentration is below the threshold, the subject may be assigned a different classification.
The skilled person can use a number of methods to derive the required threshold values for these methods. For example, the threshold may be determined from a population of normal subjects by selecting a concentration representative of the 75 th, 85 th, 90 th, 95 th or 99 th percentile of the kidney injury markers measured in such normal subjects. Alternatively, by selecting a concentration representative of the 75 th, 85 th, 90 th, 95 th or 99 th percentile of the kidney injury markers measured in such subjects, a threshold value may be determined from a population of "diseased" subjects, e.g., subjects with injury or susceptible injury (e.g., progression to ARF or some other clinical outcome, such as death, dialysis, kidney transplantation, etc.). In another alternative, the threshold may be determined from a previously measured renal injury marker in the same subject; that is, the subject's risk can be assigned using the temporal change in the subject's renal injury marker level.
However, the above discussion is not meant to imply that the kidney injury markers of the present invention must be compared to a corresponding single threshold. Methods for combining assay results may include employing multivariate logistic regression, log linear modeling, neural network analysis, n-of-m analysis, decision tree analysis, calculating marker ratios, and the like. This list is not meant to be limiting. In these methods, the composite results determined by combining the individual markers can be processed as if they were markers themselves; that is, a threshold may be determined for the composite result as described herein for a single marker and the composite result for a single patient compared to this threshold.
The ability to distinguish a particular test between two clusters can be established using ROC analysis. For example, a ROC curve established from a "first" subpopulation whose renal status is susceptible to one or more future changes and a "second" subpopulation which is less susceptible to occurrence can be used to calculate a ROC curve, the area under the curve providing a measure of the quality of the test. Preferably, the test described herein provides a ROC curve area greater than 0.5, preferably at least 0.6, more preferably 0.7, still more preferably at least 0.8, even more preferably at least 0.9, and most preferably at least 0.95.
In certain aspects, the measured concentration of one or more kidney injury markers or complexes of such markers can be treated as a continuous variable. For example, any particular concentration can be converted into a corresponding probability of the subject's future reduced renal function, the occurrence of an injury, classification, etc. In yet another alternative, the threshold may provide a level of specificity and sensitivity that is acceptable when dividing a population of subjects into "multiple populations" (bins), such as into a "first" subpopulation (e.g., a subpopulation that is prone to one or more future changes in renal status, to injury, to classification, etc.) and a "second" subpopulation that is less prone to the above-described conditions. Selecting a threshold value by one or more of the following measures of test accuracy to separate the first population from the second population:
an odds ratio of greater than 1, preferably at least about 2 or greater, or about 0.5 or less, more preferably at least about 3 or greater, or about 0.33 or less, still more preferably at least about 4 or greater, or about 0.25 or less, even more preferably at least about 5 or greater, or about 0.2 or less, and most preferably at least about 10 or greater, or about 0.1 or less;
a specificity of greater than 0.5, preferably at least about 0.6, more preferably at least about 0.7, still more preferably at least about 0.8, even more preferably at least about 0.9 and most preferably at least about 0.95, wherein the corresponding sensitivity is greater than 0.2, preferably greater than about 0.3, more preferably greater than about 0.4, still more preferably at least about 0.5, even more preferably about 0.6, still more preferably greater than about 0.7, still more preferably greater than about 0.8, more preferably greater than about 0.9 and most preferably greater than about 0.95;
a sensitivity of greater than 0.5, preferably at least about 0.6, more preferably at least about 0.7, still more preferably at least about 0.8, even more preferably at least about 0.9 and most preferably at least about 0.95, wherein the corresponding sensitivity is greater than 0.2, preferably greater than about 0.3, more preferably greater than about 0.4, still more preferably at least about 0.5, even more preferably about 0.6, still more preferably greater than about 0.7, still more preferably greater than about 0.8, more preferably greater than about 0.9 and most preferably greater than about 0.95;
a combination of at least about 75% sensitivity and at least about 75% specificity;
a positive likelihood ratio (calculated as sensitivity/(1-specificity)) of greater than 1, at least about 2, more preferably at least about 3, still more preferably at least about 5, and most preferably at least about 10; or
The negative likelihood ratio (calculated as (1-sensitivity)/specificity) is less than 1, less than or equal to about 0.5, more preferably less than or equal to about 0.3, and most preferably less than or equal to about 0.1.
The term "about" in the context of any of the above measurements refers to a given measurement value +/-5%.
Multiple thresholds may also be used to assess renal status in a subject. For example, a "first" subpopulation (susceptible to one or more future changes in renal status, the appearance of an injury, classification, etc.) and a "second" subpopulation (less susceptible to the above) may be combined into a single group. This group is then subdivided into three or more equal portions (referred to as tertiles, quartiles, quintiles, etc., depending on the number of subdivisions). The subjects were assigned odds ratios according to the sub-groups to which they were assigned. If the three-tap is considered, the lowest or highest three-tap may be used as a reference to compare other subdivisions. The odds ratio of this reference subdivision is designated as 1. The ratio of the ratios of the second three decimals is specified relative to that of the first three decimals. That is, the likelihood of someone in the second quartile suffering from one or more future changes in renal status may be three times greater than someone in the first quartile. The ratio of the ratios of the third three decimals is also specified relative to that first three decimals.
In certain embodiments, the assay method is an immunoassay. The antibody used in such an assay will specifically bind to the full-length kidney injury marker of interest, and may also bind to one or more of its "related" polypeptides, which terms will be defined below. Many immunoassay formats are known to those skilled in the art. Preferred body fluid samples are selected from urine, blood, serum, saliva, tears, and plasma.
The above method steps should not be construed as meaning that the kidney injury marker assay results are used in isolation in the methods described herein. Rather, additional variables or other clinical signs may be included in the methods described herein. For example, methods of risk stratification, diagnosis, classification, monitoring, etc., may combine the assay results with one or more variables determined for the subject selected from the group consisting of: demographic information (e.g., weight, gender, age, race), medical history (e.g., family history, surgical type, pre-existing disease such as aneurysm, congestive heart failure, preeclampsia, eclampsia, diabetes, hypertension, coronary artery disease, proteinuria, renal insufficiency, or sepsis; toxin exposure type such as exposure to NSAID, cyclosporine, tacrolimus, aminoglycoside, foscarnet, ethylene glycol, hemoglobin, myoglobin, ifosfamide, heavy metals, methotrexate, radiopaque contrast agents, or streptozotocin), clinical variables (e.g., blood pressure, body temperature, respiratory rate), risk score (APACHE score, dicret score, UA/NSTEMI risk score, Framingham risk score), glomerular filtration rate, estimated glomerular filtration rate, urinary productivity, serum or plasma creatinine concentration, blood glucose concentration, glucose concentration, Urine creatinine concentration, sodium excretion fraction, urine sodium concentration, ratio of urine creatinine to serum or plasma creatinine, urine specific gravity, urine osmolality, ratio of urine urea nitrogen to plasma urea nitrogen, ratio of plasma BUN to creatinine, renal failure index calculated as urine sodium/(urine creatinine/plasma creatinine), serum or plasma Neutrophil Gelatinase (NGAL) concentration, urine NGAL concentration, serum or plasma cystatin C concentration, serum or plasma troponin concentration, serum or plasma BNP concentration, serum or plasma NTproBNP concentration, and serum or plasma proBNP concentration. Additional measures of renal function that can be combined with the results of one or more renal injury marker assays are described below and in Harrison's renal documents of Internal Medicine, 17 th edition, McGraw Hill, New York, pp 1741-.
When more than one marker is measured, a single marker may be measured in samples taken at the same time, or may be determined from samples taken at different times (e.g., earlier or later). Individual markers may also be measured on the same or different bodily fluid samples. For example, one kidney injury marker can be measured in a serum or plasma sample and another kidney injury marker can be measured in a urine sample. Furthermore, assigning a likelihood may combine a single kidney injury marker assay result with temporal changes in one or more additional variables.
In various related aspects, the invention also relates to devices and kits for performing the methods described herein. Suitable kits include reagents sufficient to perform an assay for at least one of the kidney injury markers along with instructions for performing the threshold comparison.
In certain embodiments, the reagents for performing such assays are provided in an assay device, and such assay device may be included in such kits. Preferred reagents may include one or more solid phase antibodies, including antibodies that detect the desired biomarker target bound to a solid support. In the case of a sandwich immunoassay, such reagents may also include one or more detectably labeled antibodies, including antibodies that detect a desired biomarker target that is bound to a detectable label. Other optional elements that may be provided as part of the assay device are described below.
Detectable markers may include self-detectable molecules (e.g., fluorescent moieties, electrochemical labels, ecl (electrochemiluminescent) labels, metal chelates, colloidal metal particles, etc.) as well as molecules that can be detected indirectly by generating a detectable reaction product (e.g., an enzyme such as horseradish peroxidase, alkaline phosphatase, etc.) or by using a specific binding molecule that can be detected by itself (e.g., a labeled antibody conjugated to a second antibody, biotin, digoxigenin, maltose, oligohistidine, 2, 4-dinitrobenzene, phenyl arsenate, ssDNA, dsDNA, etc.).
The generation of the signal by the signal generating element may be performed using various optical, acoustic and electrochemical methods well known in the art. Examples of detection modes include fluorescence, radiochemical detection, reflectance, absorption, amperometry, conductance, impedance, interferometry, ellipsometry, and the like. In some of these methods, the solid phase antibody is coupled to a transducer (e.g., a diffraction grating, an electrochemical sensor, etc.) to generate a signal, while in other methods, the signal is generated by a transducer that is spatially separated from the solid phase antibody (e.g., a fluorometer that uses an excitation light source and a photodetector). This list is not meant to be limiting. Antibody-based biosensors may also be used to determine the presence or quantity of an analyte, optionally excluding marker molecules.
Detailed Description
The present invention relates to methods and compositions for diagnosing, differentially diagnosing, risk stratifying, monitoring, classifying, and determining a treatment regimen for a subject suffering from or at risk for an injury to renal function, reduced renal function, and/or acute renal failure by measuring one or more renal injury markers. In various embodiments, measured concentrations of one or more markers selected from the group consisting of C-C motif chemokine 16, C-C motif chemokine 14, and tyrosine protein kinase receptor UFO, or one or more markers related thereto, and optionally one or more additional kidney injury markers known in the art, are correlated with renal status of the subject.
For the purposes of this document, the following definitions apply:
as used herein, an "impairment of renal function" is a measured sharp (within 14 days, preferably within 7 days, more preferably within 72 hours, and still more preferably within 48 hours) measurable decrease in renal function. Such an injury can be identified, for example, by a decrease in glomerular filtration rate or estimated GFR, a decrease in urinary output, an increase in serum creatinine, an increase in serum cystatin C, a need for renal replacement therapy, and the like. An "improvement in renal function" is a sharp (within 14 days, preferably within 7 days, more preferably within 72 hours, and still more preferably within 48 hours) measurable increase in renal function measured. Preferred methods for measuring and/or estimating GFR are described below.
As used herein, "reduced renal function" is a sharp (within 14 days, preferably within 7 days, more preferably within 72 hours, and still more preferably within 48 hours) decline in renal function identified by an absolute increase in serum creatinine of greater than or equal to 0.1mg/dL (> 8.8 μmol/L), a percent increase in serum creatinine of greater than or equal to 20% (1.2-fold of baseline), or a decrease in urine output (less than 0.5ml/kg per hour is reported for oliguria).
As used herein, "acute renal failure" or "ARF" is a sharp (within 14 days, preferably within 7 days, more preferably within 72 hours, and still more preferably within 48 hours) decrease in renal function identified by an absolute increase in serum creatinine of greater than or equal to 0.3mg/dl (. gtoreq.26.4. mu. mol/l), a percent increase in serum creatinine of greater than or equal to 50% (1.5 fold of baseline), or a decrease in urine output (less than 0.5ml/kg per hour for at least 6 hours of urine recorded). This term is synonymous with "acute kidney injury" or "AKI".
In this regard, the skilled artisan will appreciate that the signal obtained by the immunoassay is a direct result of the complex formed between the antibody or antibodies and the target biomolecule (i.e., analyte) and the polypeptide containing the requisite epitope for binding to the antibody. While such assays can detect full-length biomarkers and express the assay result as the concentration of the biomarker of interest, the signal from the assay is actually the result of all such "immunoreactive" polypeptides present in the sample. Expression of biomarkers can also be determined by methods other than immunoassays, including protein measurements (such as dot blot, western blot, chromatography, mass spectrometry, etc.) and nucleic acid measurements (mRNA quantification). This list is not meant to be limiting.
As used herein, the term "C-C motif chemokine 16" refers to one or more polypeptides (human sequence: Swiss-Prot O15467(SEQ ID NO:1)) present in a biological sample derived from a precursor of C-C motif chemokine 16:
the following domains in C-C motif chemokine 16 have been identified:
residue length Domain ID
1-2323 Signal peptide
24-12097C-C motif chemokine 16
As used herein, the term "C-C motif chemokine 14" refers to one or more polypeptides (human sequence: Swiss-Prot Q16627(SEQ ID NO:1)) present in a biological sample derived from a precursor of C-C motif chemokine 14:
the following domains in C-C motif chemokine 14 have been identified:
as used herein, the term "tyrosine protein kinase receptor UFO" refers to one or more polypeptides present in a biological sample derived from a precursor of tyrosine protein kinase receptor UFO (human sequence: Swiss-Prot P30530(SEQ ID NO:1)):
in certain embodiments, the tyrosine protein kinase receptor UFO assay detects one or more soluble forms of tyrosine protein kinase receptor UFO. Tyrosine protein kinase receptor UFO is a single-pass membrane protein with an extracellular domain, which may be present in the tyrosine protein kinase receptor UFO form of tyrosine protein kinase receptor UFO produced by proteolytic cleavage of the membrane-bound form or by additional splicing. In the case of immunoassays, one or more antibodies that bind to an epitope within the extracellular domain can be used to detect these tyrosine protein kinase receptor UFO forms. The following domains of the tyrosine protein kinase receptor UFO have been identified:
as used herein, the term "correlating a signal to the presence or amount of an analyte" reflects this understanding. The assay signal is typically correlated to the presence or amount of analyte by using a standard curve calculated from known concentrations of the analyte of interest. As the term is used herein, an assay is "configured to detect" an analyte if the assay can produce a detectable signal indicative of the presence or amount of the analyte at a physiologically relevant concentration. Since antibody epitopes are about 8 amino acids, an immunoassay configured to detect a marker of interest will also detect polypeptides associated with the marker sequence, as long as those polypeptides contain the epitope required to bind to the antibody used in the assay.
The term "relevant marker" as used herein in reference to a biomarker (such as one of the kidney injury markers described herein) refers to one or more fragments, variants, etc. of a particular marker or its biosynthetic precursor, which can be detected as a replacement for the marker itself or as a separate biomarker. The term also refers to one or more polypeptides present in a biological sample derived from the complexation of biomarker precursors with additional substances (such as binding proteins, receptors, heparin, lipids, sugars, etc.).
The term "positive going" marker as used herein refers to a marker that is determined to be elevated in a subject having a disease or disorder relative to a subject not having the disease or disorder. The term "negative going" marker as used herein refers to a marker that is determined to be decreased in a subject having a disease or disorder relative to a subject not having the disease or disorder.
The term "subject" as used herein refers to a human or non-human organism. Thus, the methods and compositions described herein may be applicable to both human and veterinary disease. In addition, while the subject is preferably a living organism, the invention described herein can be used for post mortem analysis as well. The preferred subject is a human, and most preferably is a "patient," which as used herein refers to a living human who is receiving medical care for a disease or condition. This includes persons not suffering from the defined disease who are studied for pathological signs.
Preferably, the analyte is measured in the sample. Such a sample may be obtained from a subject, or may be obtained from biological material intended to be provided to a subject. For example, a sample may be obtained from a kidney being evaluated for a possible transplant in a subject, and analyte measurements are used to evaluate the kidney for an existing injury. Preferably the sample is a body fluid sample.
The term "bodily fluid sample" as used herein refers to a sample of bodily fluid obtained for the purpose of diagnosis, prognosis, classification or evaluation of a subject of interest, such as a patient or transplant donor. In certain embodiments, such samples may be obtained for the purpose of determining the outcome of an ongoing condition or the effect of a treatment regimen on a condition. Preferred bodily fluid samples include blood, serum, plasma, cerebrospinal fluid, urine, saliva, sputum, and pleural effusion. In addition, one skilled in the art will recognize that certain bodily fluid samples may be more easily analyzed after fractionation or purification procedures (e.g., separation of whole blood into serum or plasma components).
The term "diagnosis" as used herein refers to a method by which a skilled person can estimate and/or determine the probability ("likelihood") of whether a patient has or does not have a given disease or condition. In the context of the present invention, "diagnosis" includes the use of the results of an assay (most preferably an immunoassay) to arrive at a diagnosis (that is, the occurrence or non-occurrence) of acute kidney injury or ARF in a subject from which a sample is obtained and assessed for a kidney injury marker of the present invention, optionally along with other clinical characteristics. "determining" such a diagnosis is not meant to imply that the diagnosis is 100% accurate. Many biomarkers are indicative of a variety of conditions. An experienced clinician would not use biomarker results with a vacuum of information, but would use test results with other clinical signs to arrive at a diagnosis. Thus, a measured biomarker level on one side of the predetermined diagnostic threshold relative to a measured level on the other side of the predetermined diagnostic threshold indicates a greater likelihood of disease occurring in the subject.
Similarly, a prognostic risk signal represents the probability ("likelihood") that a given process or outcome will occur. The level or change in level of a prognostic indicator, which in turn is associated with an increased incidence of morbidity (e.g., worsening renal function, future ARF, or death), is considered to be an "indication of increased likelihood" of an adverse outcome for the patient.
Marker assay
In general, immunoassays comprise contacting a sample containing or suspected of containing a biomarker of interest with at least one antibody that specifically binds to the biomarker. A signal is then generated indicative of the presence or amount of a complex formed by binding the polypeptide in the sample to the antibody. The signal is then correlated with the presence or amount of the biomarker in the sample. Numerous methods and devices for detecting and analyzing biomarkers are well known to the skilled person. See, for example, U.S. patent 6,143,576; 6,113,855; 6,019,944, respectively; 5,985,579, respectively; 5,947,124, respectively; 5,939,272, respectively; 5,922,615, respectively; 5,885,527, respectively; 5,851,776, respectively; 5,824,799, respectively; 5,679,526, respectively; 5,525,524, respectively; and 5,480,792, and the institute Handbook, David Wild, Stockton Press, New York, 1994, each of which is hereby incorporated by reference in its entirety, including all tables, figures and claims.
Assay devices and methods known in the art can use labeled molecules in various sandwich assays, competitive assays, or non-competitive assay formats to generate a signal related to the presence or amount of a biomarker of interest. Suitable assay formats also include chromatography, mass spectrometry, and western "blotting" methods. In addition, certain methods and devices, such as biosensors and optical immunoassays, can be employed to determine the presence or amount of an analyte without the need for a labeling molecule. See, for example, U.S. Pat. nos. 5,631,171; and 5,955,377, each of which is hereby incorporated by reference herein, including all patents, cited hereinTables, drawings and claims. Those skilled in the art will also recognize that including but not limited to Beckman
Antibodies or other polypeptides may be immobilized to a variety of solid supports for assays. Solid phases that can be used to immobilize specific binding members include those developed and/or used as solid phases in solid phase binding assays. Examples of suitable solid phases include membrane filters, cellulose-based papers, beads (including polymeric particles, latex particles, and paramagnetic particles), glass, silicon wafers, microparticles, nanoparticles, TentaGels, AgroGels, PEGA gels, SPOCC gels, and multiwell plates. The assay strips may be prepared by coating the antibody or antibodies in an array on a solid support. Such strips may then be dipped into a test sample and then rapidly processed through washing and detection steps to produce a measurable signal, such as a developed spot. The antibody or other polypeptide may bind to a particular region of the assay device by direct conjugation to the surface of the assay device or by indirect binding. In the latter instance, the antibody or other polypeptide may be immobilized on a particle or other solid support, and the solid support is immobilized on the surface of the device.
Bioassays require detection methods, and one of the most common methods for result quantification is the conjugation of a detectable label to a protein or nucleic acid that has an affinity for one of the components in the biological system under study. The detectable label may include a molecule that is itself detectable (e.g., a fluorescent moiety, an electrochemical label, a metal chelate, etc.); and molecules that can be detected indirectly by producing a detectable reaction product (e.g., an enzyme such as horseradish peroxidase, alkaline phosphatase, etc.) or by a specific binding molecule that can be detectable by itself (e.g., biotin, digoxigenin, maltose, oligohistidine, 2, 4-dinitrobenzene, phenyl arsenate, ssDNA, dsDNA, etc.).
The preparation of solid phase and detectably labeled conjugates often involves the use of chemical cross-linking agents. The crosslinking agent contains at least two reactive groups and is generally divided into homofunctional crosslinking agents (containing the same reactive groups) and heterofunctional crosslinking agents (containing different reactive groups). Homobifunctional crosslinkers which are coupled via amines, thiols or non-specific reactions are available from many commercial sources. Maleimides, alkyl and aryl halides, α -acyl halides and pyridyl disulfides are thiol-reactive groups. Maleimides, alkyl and aryl halides and α -acyl halides react with thiols to form mercaptoh linkages, while pyridyl disulfides react with thiols to produce mixed sulfides. The pyridyl disulfide product is cleavable. Imidoesters are also useful for protein-protein crosslinking. A variety of heterobifunctional crosslinkers (each combined with different attributes for successful conjugation) are commercially available.
In certain aspects, the invention provides kits for analyzing the described kidney injury markers. The kit comprises reagents for analyzing at least one test sample comprising at least one antibody to a kidney injury marker. The kit may further comprise means and instructions for performing one or more of the diagnostic and/or prognostic correlations described herein. Preferred kits will include an antibody pair for performing a sandwich assay, or a labeling substance for performing a competition assay, against the analyte. Preferably, the antibody pair comprises a first antibody conjugated to a solid phase and a second antibody conjugated to a detectable label, wherein the first and second antibodies each bind to a kidney injury marker. Most preferably, the antibodies are each monoclonal antibodies. Instructions for using the kits and performing the correlation may be in the form of indicia referring to any written or recorded material that is attached to or otherwise associated with the kits at any time during manufacture, shipping, sale, or use of the kits. For example, the term indicia encompasses advertising leaflets and brochures, packaging materials, instructions, audio or video tapes, computer discs, and text printed directly on the kit.
Antibodies
The term "antibody" as used herein refers to a peptide or polypeptide derived from, mimicking or substantially encoded by one or more immunoglobulin genes or fragments thereof, which is capable of specifically binding an antigen or epitope. See, e.g., Fundamental Immunology, 3 rd edition, ed. w.e.paul, Raven Press, n.y. (1993); wilson (1994; J.Immunol.methods 175: 267-273; yarmush (1992) j. biochem. biophysis. methods25:85-97 the term antibody includes an antigen-binding portion that retains the ability to bind antigen, i.e., "antigen binding sites" (e.g., fragments, subsequences, Complementarity Determining Regions (CDRs)), including: (i) (ii) a Fab fragment of a heavy chain, it is a monovalent fragment consisting of the VL, VH, CL and CHl domains; (ii) a fragment of F (ab')2, which is a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; (iii) an Fd fragment consisting of the VH and CHl domains; (iv) (ii) an Fv fragment consisting of the VL and VH domains of a single arm of an antibody; (v) dAb fragments consisting of VH domains (Ward et al, (1989) Nature 341: 544-546); single chain antibodies are also included in the term "antibody" for reference.
The antibodies described herein for use in immunoassays preferably specifically bind to the kidney injury markers of the present invention. The term "specifically binds" is not intended to indicate that an antibody binds exclusively to its intended target, as the antibody binds to any polypeptide that exhibits an epitope bound by the antibody, as described above. Rather, an antibody "specifically binds" only when: the affinity of the antibody for its desired target is greater than about 5-fold greater than the affinity of the antibody for non-target molecules that do not display the appropriate epitope. PreferablyThe affinity of the antibody for the target molecule will be at least about 5-fold, preferably 10-fold, more preferably 25-fold, even more preferably 50-fold and most preferably 100-fold or greater than its affinity for non-target molecules. In preferred embodiments, preferred antibodies are present in an amount of at least about 107M-1And preferably between about 108M-1To about 109M-1About 109M-1To about 1010M-1Or about 1010M-1To about 1012M-1Affinity binding between.
Affinity was calculated as Kd＝koff/kon(koffIs the dissociation rate constant, KonIs an association rate constant, and KdIs an equilibrium constant). Affinity can be determined at equilibrium by measuring the fraction (r) of binding of the labeled ligand at various concentrations (c). Data were plotted using Scatchard (Scatchard) equation: r/c ═ K (n-r): wherein r is the number of moles of binding ligand/moles of receptor in the equilibrium state; c is the free ligand concentration at equilibrium; k ═ equilibrium association constant; and n is the number of ligand binding sites per receptor molecule. By graphical analysis, r/c is plotted on the Y-axis compared to r on the X-axis, thereby generating a scatchard plot. Antibody affinity measurements by scatchard analysis are well known in the art. See, e.g., van Erp et al, j.immunoassay 12: 425-43, 1991; nelson and Griswold, comput. methods Programs biomed.27: 65-8, 1988.
The term "epitope" refers to an antigenic determinant capable of specific binding to an antibody. Epitopes are usually composed of chemically active surface groups of molecules, such as amino acids or sugar side chains, and usually have specific three-dimensional structural characteristics, as well as specific charge characteristics. Conformational and non-conformational epitopes differ by: in the presence of denaturing solvents, binding to conformational epitopes, but not to non-conformational epitopes, is lost.
Numerous publications discuss the use of phage display technology to generate and screen libraries of polypeptides for binding to selected analytes. See, e.g., Cwirla et al, Proc.Natl.Acad.Sci.USA 87, 6378-82, 1990; devlin et al, Science 249, 404-6, 1990, Scott and Smith, Science 249, 386-88, 1990; and Ladner et al, U.S. patent No. 5,571,698. The basic concept of the phage display method is to establish a physical association between the DNA encoding the polypeptide to be screened and the polypeptide. This physical association is provided by the phage particle which displays the polypeptide as part of a capsid that encapsulates the phage genome encoding the polypeptide. Establishing a physical association between a polypeptide and its genetic material allows for large-scale screening of a very large number of phage carrying different polypeptides simultaneously. Phage displaying polypeptides with affinity for a target bind to the target and are enriched by affinity screening for the target. The identity of the polypeptides displayed from these phage can be determined from their respective genomes. Using these methods, polypeptides identified as having binding affinity for a desired target can then be synthesized in large quantities by conventional means. See, for example, U.S. patent No. 6,057,098, which is hereby incorporated by reference in its entirety, including all tables, figures, and claims.
Antibodies produced by these methods can then be selected by: the purified polypeptide of interest is first screened for affinity and specificity and, if desired, the results of the affinity and specificity of the antibody are compared to the polypeptide that needs to be excluded from binding. The screening procedure may include immobilizing the purified polypeptide in separate wells of a microtiter plate. The solution containing the potential antibody or group of antibodies is then placed into the respective microtiter wells and incubated for about 30 minutes to 2 hours. The microtiter wells are then washed, and labeled secondary antibody (e.g., anti-mouse antibody conjugated to alkaline phosphatase if the antibody produced is mouse) is added to each well and incubated for about 30 minutes and then washed. A substrate is added to each well and in the presence of antibodies to the immobilized polypeptide, a color reaction will occur.
The antibodies so identified can then be further analyzed for affinity and specificity in the chosen assay design. In developing immunoassays for target proteins, the purified target proteins serve as standards against which the sensitivity and specificity of immunoassays using antibodies that have been selected are judged. Since the binding affinity of various antibodies can vary; certain antibody pairs (e.g., in sandwich assays) can spatially interfere with each other, etc., and the assay performance of an antibody can be a more important measure than absolute antibody affinity and specificity.
Determination of correlation
The term "associated" as used herein with reference to the use of a biomarker refers to comparing the presence or amount of a biomarker in a patient with the presence or amount of a biomarker in a human known to have or known to be at risk of a given condition, or a human known not to have a given condition. This often takes the form: the result of the determination in the form of the concentration of the biomarker is compared to a predetermined threshold value selected to indicate the occurrence or non-occurrence of the disease or the likelihood of some future outcome.
Selecting a diagnostic threshold includes, among other things, considering the probability of disease, the distribution of true and false diagnoses at different test thresholds, and an estimate of the outcome of a treatment based on the diagnosis (or treatment failure). For example, when considering the administration of specific therapies that are highly effective and have reduced levels of risk, little testing is required as clinicians can accept most of the diagnostic uncertainty. On the other hand, clinicians often require a higher degree of certainty in diagnosis where treatment options are less effective and more risky. Therefore, cost/benefit analysis is involved in selecting a diagnostic threshold.
Suitable thresholds may be determined in various ways. For example, one proposed threshold for using cardiac troponin for diagnosis of acute myocardial infarction is the 97.5 th percentile of concentrations observed in the normal population. Another approach may be to look at a series of samples from the same patient, where the previous "baseline" results were used to monitor temporal changes in biomarker levels.
Population studies can also be used to select decision thresholds. Receiver operating characteristics ("ROC") come from the field of signal detection theory developed during world war ii for analyzing radar images, and ROC analysis is often used to select a threshold that best distinguishes the "diseased" subpopulation from the "non-diseased" subpopulation. In this case, false positives occur when one tests positive but does not actually have the disease. On the other hand, when people test negative (indicating that they are healthy), they are actually ill and false negatives appear. To plot the ROC curve, the True Positive Rate (TPR) and False Positive Rate (FPR) were measured while the decision threshold was continuously varied. Since TPR is equivalent to sensitivity and FPR is equivalent to 1-specificity, the ROC curve is sometimes referred to as a sensitivity-to- (1-specificity) curve. A perfect test will have an area under the ROC curve of 1.0; the random test will have an area of 0.5. The threshold is selected to provide an acceptable level of specificity and sensitivity.
In this context, "diseased" is intended to refer to a population having a characteristic (presence of a certain disease or condition, or occurrence of a certain outcome), while "not diseased" is intended to refer to a population lacking the characteristic. While a single decision threshold is the simplest application of this approach, multiple decision thresholds may be used. For example, below a first threshold, a relatively high degree of confidence may be assigned to the absence of disease, and above a second threshold, a relatively high degree of confidence may also be assigned to the presence of disease. Between these two thresholds can be considered intermediate states. This is meant to be exemplary in nature only.
In addition to threshold comparisons, other methods for correlating the assay results with patient classification (occurrence or non-occurrence of disease, likelihood of outcome, etc.) include decision trees, rule sets, Bayesian methods, and neural network methods. The methods may generate a probability value representing the degree to which the subject belongs to one of a plurality of classifications.
The measurement of the accuracy of the test can be measured as described by Fischer et al, Intensive Care Med.29: 1043-51, 2003 and is used to determine the effectiveness of a given biomarker. These metrics include sensitivity and specificity, predictive value, likelihood ratio, diagnostic ratio, and ROC curve area. The area under the curve ("AUC") of the ROC plot is equal to the probability that the classifier will make randomly selected positive cases higher than randomly selected negative cases. Thus, the area under the ROC curve can be considered to be equivalent to the Mann-Whitney U test, which tests for the median difference between the scores obtained in the two groups considered (if the groups have consecutive data), or to the Wilcoxon rank test.
As discussed above, suitable tests may show one or more of the following results for these different measurements: a specificity of greater than 0.5, preferably at least 0.6, more preferably at least 0.7, still more preferably at least 0.8, even more preferably at least 0.9 and most preferably at least 0.95, wherein the corresponding sensitivity is greater than 0.2, preferably greater than 0.3, more preferably greater than 0.4, still more preferably at least 0.5, even more preferably 0.6, still more preferably greater than 0.7, still more preferably greater than 0.8, more preferably greater than 0.9 and most preferably greater than 0.95; a sensitivity of greater than 0.5, preferably at least 0.6, more preferably at least 0.7, still more preferably at least 0.8, even more preferably at least 0.9 and most preferably at least 0.95, wherein the corresponding specificity is greater than 0.2, preferably greater than 0.3, more preferably greater than 0.4, still more preferably at least 0.5, even more preferably 0.6, still more preferably greater than 0.7, still more preferably greater than 0.8, more preferably greater than 0.9 and most preferably greater than 0.95; at least 75% sensitivity, in combination with at least 75% specificity; a ROC curve area greater than 0.5, preferably at least 0.6, more preferably 0.7, still more preferably at least 0.8, even more preferably at least 0.9, and most preferably at least 0.95; the ratio of ratios is different from 1, preferably at least about 2 or greater or about 0.5 or less, more preferably at least about 3 or greater or about 0.33 or less, still more preferably at least about 4 or greater or about 0.25 or less, even more preferably at least about 5 or greater or about 0.2 or less and most preferably at least about 10 or greater or about 0.1 or less; a positive likelihood ratio (calculated as sensitivity/(1-specificity)) of greater than 1, at least 2, more preferably at least 3, still more preferably at least 5, and most preferably at least 10; and/or a negative likelihood ratio (calculated as (1-sensitivity)/specificity) of less than 1, less than or equal to 0.5, more preferably less than or equal to 0.3, and most preferably less than or equal to 0.1.
Additional clinical signs may be combined with the renal injury marker assay results of the present invention. These include other biomarkers associated with renal status. Examples include the following (listed are common biomarker names followed by the Swiss-Prot accession numbers for the biomarkers or their parents): actin (P68133); adenosine deaminase binding protein (DPP4, P27487); alpha-1-acid glycoprotein 1 (P02763); α -1-microglobulin (P02760); albumin (P02768); angiotensinogenase (Renin, P00797); annexin a2 (P07355); β -glucuronidase (P08236); b-2-microglobulin (P61769); beta-galactosidase (P16278); BMP-7 (P18075); brain natriuretic peptides (proBNP, BNP-32, NTproBNP; P16860); calcium-binding protein beta (S100-beta, P04271); carbonic anhydrase 9 (Q16790); casein kinase 2 (P68400); clusterin (P10909); complement C3 (P01024); complement-rich protein (CYR61, O00622); cytochrome (P99999); epidermal growth factor (EGF, P01133); endothelin-1 (P05305); extranuclear fetuin-a (P02765); fatty acid-binding proteins, heart (FABP3, P05413); fatty acid-binding protein, liver (P07148); ferritin (light chain, P02792; heavy chain P02794); fructose-1, 6-bisphosphatase (P09467); GRO-alpha (CXCL1, (P09341), growth hormone (P01241), hepatocyte growth factor (P14210), insulin-like growth factor I (P05019), immunoglobulin G, immunoglobulin light chain (kappa and lambda), interferon gamma (P01308), lysozyme (P61626), interleukin-1 alpha (P01583), interleukin-2 (P60568), interleukin-4 (P05112), interleukin-9 (P15248), interleukin-12P 40(P29460), interleukin-13 (P35225), interleukin-16 (Q14005), L1 cell adhesion molecule (P32004), lactate dehydrogenase (P00338), alanine aminopeptidase (P28838), hypnotic protein A (Meprin A) -alpha subunit (Q19), hypnotic protein A-beta subunit (Q16820), midMIP (MidMIPie) (P21741), CX 2-alpha (CX3624, MMP 2, MMP 8653-P1687-EP 1689580), neutrophilic growth factor P08631 (MMP 16880), interleukin-16 (P08280), interleukin-16 (P16880), and its use Desmin (O14788); renal papillary antigen 1(RPA 1); renal papillary antigen 2(RPA 2); retinol binding protein (P09455); ribonucleases; s100 calcium-binding protein a6 (P06703); serum amyloid P component (P02743); sodium/hydrogen exchanger isoform (NHE3, P48764); spermidine/spermine N1-acetyltransferase (P21673); TGF-. beta.1 (P01137); transferrin (P02787); trefoil factor 3(TFF3, Q07654); toll-like protein 4 (O00206); total protein; tubulointerstitial nephritis antigen (Q9UJW 2); uromodulin (Tamm-Horsfall protein, P07911).
Adiponectin (Q15848) for risk stratification purposes; alkaline phosphatase (P05186); aminopeptidase N (P15144); calbindin D28k (P05937); cystatin C (P01034); 8 subunit of F1FO atpase (P03928); gamma-glutamyl transferase (P19440); GSTa (α -glutathione-S-transferase, P08263); GSTpi (glutathione-S-transferase P; GST-like-pi; P09211); IGFBP-1 (P08833); IGFBP-2 (P18065); IGFBP-6 (P245792); integral membrane protein 1(Itm1, P46977); interleukin-6 (P05231); interleukin-8 (P10145); interleukin-18 (Q14116); IP-10(10kDa interferon-gamma-inducing protein, P02778); IRPR (IFRD1, O00458); isovaleryl-CoA dehydrogenase (IVD, P26440); I-TAC/CXCL11 (O14625); keratin 19 (P08727); kim-1 (hepatitis a virus cell receptor 1, O43656); l-arginine Glycine amidinotransferase (P50440); leptin (P41159); lipocalin 2(NGAL, P80188); MCP-1 (P13500); MIG (gamma interferon-inducible monokine Q07325); MIP-1a (P10147); MIP-3a (P78556); MIP-1 β (P13236); MIP-1d (Q16663); NAG (N-acetyl- β -D-glucosaminidase, P54802); organic ion transporters (OCT2, O15244); osteoprotegerin (O14788); p8 protein (O60356); plasminogen activator inhibitor 1(PAI-1, P05121); anterior ANP (1-98) (P01160); protein phosphatase 1-beta (PPI-beta, P62140); rab GDI- β (P50395); renal kinins (P06870); RT1.B-1 (. alpha.) chain of integral membrane protein (Q5Y7A 8); soluble tumor necrosis factor receptor superfamily member 1A (sTNFR-I, P19438); soluble tumor necrosis factor receptor superfamily member 1B (sTNFR-II, P20333); tissue inhibitor of metalloproteinases 3(TIMP-3, P35625); uPAR (Q03405) can be combined with the kidney injury marker assay results of the present invention.
Other clinical markers that can be combined with the kidney injury marker assay results of the invention include demographic information (e.g., weight, gender, age, race), medical history (e.g., family history, type of surgery, pre-existing disease such as aneurysm, congestive heart failure, preeclampsia, eclampsia, diabetes, hypertension, coronary artery disease, proteinuria, renal insufficiency, or sepsis), toxin exposure type (e.g., NSAID, cyclosporine, tacrolimus, aminoglycoside, foscarnet, ethylene glycol, hemoglobin, myoglobin, ifosfamide, heavy metals, methotrexate, radiopaque contrast agents, or streptozotocin), clinical variables (e.g., blood pressure, temperature, respiration rate), risk score (APACHE score, pret score, UA/NSTEMI risk score, Framingham risk score), total urine protein measurement, total protein measurement, clinical variables (e.g., blood pressure, temperature, respiration rate), risk score (APACHE score, dict score, UA/NSTEMI risk score, Framingham risk score), urinary total protein measurement, Glomerular filtration rate, estimated glomerular filtration rate, urine production rate, serum or plasma creatinine concentration, renal papillary antigen 1(RPA1) measurement; renal papillary antigen 2(RPA2) measurement; urine creatinine concentration, sodium excretion fraction, urine sodium concentration, urine creatinine to serum or plasma creatinine ratio, urine specific gravity, urine osmolarity, urine urea nitrogen to plasma urea nitrogen ratio, plasma BUN to creatinine ratio, and/or renal failure index calculated as urine sodium/(urine creatinine/plasma creatinine). Additional measures of renal function that can be combined with the results of the renal injury marker assay are described below and in Harrison's catalysis of Internal Medicine, 17 th edition, McGraw Hill, New York, pp 1741-.
Combining the assay results/clinical signs in this manner may include using multivariate logistic regression, log-linear modeling, neural network analysis, n-of-m analysis, decision tree analysis, and the like. This list is not meant to be limiting.
Diagnosis of acute renal failure
As noted above, the terms "acute renal (or renal (kidney)) injury" and "acute renal (or kidney) failure" as used herein are defined, in part, by changes in serum creatinine from a baseline value. Most ARF definitions share common elements including the use of serum creatinine and the usual amount of urine excreted. The patient may present with renal dysfunction, and no baseline measure of renal function is available for this comparison. In this case, the serum creatinine baseline value can be estimated by assuming that the patient initially has a normal GFR. Glomerular Filtration Rate (GFR) is the volume of fluid filtered from the glomerular capillaries of the kidney into the Bowman's capsule per unit time. Glomerular Filtration Rate (GFR) can be calculated by measuring any chemical that has a stable level in the blood and is freely filtered but not reabsorbed or secreted by the kidneys. GFR is usually expressed in units of ml/min:
by normalization of the GFR to the body surface area, it can be assumed that every 1.73m2A GFR of about 75ml/min to 100 ml/min. Thus, the measured ratio is the amount of material in the urine derived from the calculable amount of blood.
Glomerular filtration rate (GFR or eGFR) can be calculated or estimated using several different techniques. However, in clinical practice, creatinine clearance is used to measure GFR. Creatinine is naturally produced by the body (creatinine is a metabolite of creatine that is found in muscle). It is freely filterable by the glomeruli, but very small amounts are actively secreted by the tubules, resulting in creatinine clearance overestimates by 10% -20% over actual GFR. This margin of error is acceptable in view of the ease of measuring creatinine clearance.
If the urine concentration (U) of creatinineCr) Urinary flow rate (V) and plasma concentration of creatinine (P)Cr) The values are known, and creatinine clearance (CCr) can be calculated. Creatinine clearance can also be considered to be its excretion rate (U) because the product of urine concentration and urine flow rate yields the excretion rate of creatinineCrX V) divided by its plasma concentration. This is mathematically generally expressed as:
urine is typically collected for 24 hours, from the empty bladder in the morning to the contents of the bladder in the next morning, and then a comparative blood test is performed:
to allow comparison of results between persons of different sizes, the CCr is usually corrected for Body Surface Area (BSA) and expressed as ml/min/1.73m2 compared to persons of average size. While most adults have BSA approaching 1.7(1.6-1.9), very fat or very thin patients should have their CCr corrected for their actual BSA:
the accuracy of creatinine clearance measurements is limited (even when collection is complete) because creatinine secretion increases with decreasing Glomerular Filtration Rate (GFR) and thus results in less elevation of serum creatinine. Creatinine excretion is therefore much larger than the filtration load, resulting in a possible overestimation of GFR (up to a two-fold difference). However, for clinical purposes, it is important to determine whether renal function is stable or getting worse or better. This is usually determined by monitoring serum creatinine alone. Similar to creatinine clearance, serum creatinine will not accurately reflect GFR under non-steady state conditions of ARF. However, the degree of change in serum creatinine from baseline will reflect changes in GFR. Serum creatinine is easy and convenient to measure and is specific to renal function.
For the purpose of determining the urine output in mL/kg/hour, it is sufficient to collect urine every hour and measure it. Minor modifications to the RIFLE voiding criteria have been described where, for example, only 24 hour cumulative voiding is obtained without providing patient weight. For example, Bagshaw et al, nephrol. 1203-: <35mL/h (risk), <21mL/h (injury), or <4mL/h (failure).
Selecting a treatment regimen
Once a diagnosis is obtained, the clinician can readily select a treatment regimen appropriate for the diagnosis, such as initiating renal replacement therapy, removing delivery of compounds known to damage the kidney, kidney transplantation, delaying or avoiding procedures known to damage the kidney, altering the administration of diuretics, initiating targeted instructional therapy, and the like. The skilled artisan is aware of suitable treatments for a variety of diseases discussed in connection with the diagnostic methods described herein. See, for example, Merck Manual of Diagnosis and Therapy, 17 th edition, Merck research Laboratories, Whitehouse Station, NJ, 1999. Furthermore, as the methods and compositions described herein provide prognostic information, the markers of the invention can be used to monitor the course of treatment. For example, an improvement or worsening in the prognostic status can indicate the effectiveness or ineffectiveness of a particular therapy.
Those skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The examples provided herein represent preferred embodiments, are exemplary, and are not intended as limitations on the scope of the invention.
Example 1: sample collection for contrast-induced nephropathy
The purpose of this sample collection study is to collect plasma and urine samples and clinical data from patients before and after receiving intravascular contrast agents. Approximately 250 adults undergoing a radiographic/angiographic procedure (involving intravascular administration of an iodinated contrast agent) were recruited. To be entered into the study, each patient must meet all of the following inclusion criteria, and not all of the following exclusion criteria:
inclusion criteria
Males and females 18 years old or older;
subject to a radiographic/angiographic procedure involving intravascular administration of a contrast agent (such as a CT scan or coronary intervention);
hospitalization is expected to be at least 48 hours after contrast administration.
It is possible and desirable to provide written consent for participation in the study and to comply with all study procedures.
Exclusion criteria
A renal transplant recipient;
acute deterioration of renal function prior to the imaging procedure;
dialysis already received (acute or chronic) or acute at the time of enrollment;
anticipated to undergo a major surgical procedure (such as involving cardiopulmonary bypass) or another imaging procedure that experiences significant risk of further renal injury from the contrast agent within 48 hours after administration of the contrast agent;
interventional clinical studies with experimental therapy were engaged within the previous 30 days;
infection with Human Immunodeficiency Virus (HIV) or hepatitis virus is known.
Immediately prior to the first administration of contrast (and after hydration of any pre-procedure), EDTA anticoagulated blood samples (10mL) and urine samples (10mL) were collected from each patient. Blood and urine samples were then collected at 4(± 0.5), 8(± 1), 24(± 2)48(± 2) and 72(± 2) hours after the last administration of contrast agent during the index contrast procedure. These study blood samples are processed into plasma at the clinical site, frozen and delivered to the asset Medical, inc., San Diego, ca.
Serum creatinine was assessed at 4 (+ -0.5), 8 (+ -1), 24 (+ -2), and 48 (+ -2)) and 72 (+ -2) hours immediately prior to (after hydration of any preceding procedure) and after the last administration of contrast agent (ideally, while obtaining study samples). In addition, the status of each patient through day 30 was assessed for additional serum and urine creatinine measurements, need for dialysis, hospitalization status, and adverse clinical outcomes (including death).
Prior to administration of the contrast agent, the risk of each patient is assigned based on the following assessments: systolic pressure<80mm Hg is 5 points; the intra-arterial balloon pump is 5 points; congestive heart failure (grade III-IV or history of pulmonary edema) 5 points; age (age)>4 points at 75 years old; hematocrit level<39% (of men),<35% (female) to 3 points; diabetes mellitus is 3 points; contrast agent volume 1 point per 100 mL; serum creatinine levels>1.5g/dL 4 points or estimated GFR 40-60 mL/min/1.73m22 spots, 20-40 mL/min/1.73m2The number of the points is 4, namely,<20mL/min/1.73m26 points. The risks specified are as follows: CIN and risk of dialysis: total of 5 points or less ═ CIN risk-7.5%, dialysis risk-0.04%; total 6-10 points-14% CIN risk, dialysis risk-0.12%; total 11-16 points-CIN risk-26.1%, dialysis risk-1.09%; in all>16 points-57.3% risk of CIN, 12.8% risk of dialysis.
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