Methods and compositions for diagnosis and prognosis of renal injury and renal failure

1 . A method of treating a subject for acute kidney injury, the method comprising:

performing an assay configured to detect Chitinase-3-like protein 1 in a body fluid sample obtained from the subject to provide an assay result, wherein assay results are combined using multivariate logistical regression, loglinear modeling, neural network analysis, n-of-m analysis, decision tree analysis, calculating ratios of markers, or a combination thereof;

correlating the assay result to an increased likelihood of the subject having persistent acute kidney injury with a minimum RIFLE stage of I or F over a period of at least 24 hours beginning within 7 days after the sample was obtained, by:

comparing the assay result to a threshold value obtained from a population study, wherein the threshold separates the population into a first subpopulation above the threshold and a second subpopulation at or below the threshold, the first subpopulation being at an increased likelihood of having persistent acute kidney injury relative to the second subpopulation, and

assigning the subject to the first subpopulation; and

treating the subject, wherein the treatment comprises renal replacement therapy, withdrawing delivery of compounds that are known to be damaging to the kidney, delaying procedures that are known to be damaging to the kidney, modifying diuretic administration, or administering one or more agents or measured volumes of fluid to restore normal fluid levels, electrolyte levels, or hemodynamics; and

wherein by correlating and comparing the assay results, the above method discriminates between persistent and non-persistent forms of acute kidney injury (AKI).

2 . The method of claim 1 , wherein the subject is in RIFLE stage R acute kidney injury when the sample is obtained.

3 . The method of claim 1 , wherein the subject is in RIFLE stage I acute kidney injury when the sample is obtained.

4 . The method of claim 1 , wherein the subject is in RIFLE stage F acute kidney injury when the sample is obtained.

5 . The method of claim 1 , wherein the increased likelihood is of the subject having persistent acute kidney injury with a minimum RIFLE stage of I over the period of at least 24 hours.

6 . The method of claim 5 , wherein the subject is in RIFLE stage R acute kidney injury when the sample is obtained.

7 . The method of claim 5 , wherein the subject is in RIFLE stage I acute kidney injury when the sample is obtained.

8 . The method of claim 5 , wherein the subject is in RIFLE stage F acute kidney injury when the sample is obtained.

9 . The method of claim 1 , wherein the increased likelihood is of the subject having persistent acute kidney injury with a minimum RIFLE stage of F over the period of at least 24 hours.

10 . The method of claim 9 , wherein the subject is in RIFLE stage R acute kidney injury when the sample is obtained.

11 . The method of claim 9 , wherein the subject is in RIFLE stage I acute kidney injury when the sample is obtained.

12 . The method of claim 9 , wherein the subject is in RIFLE stage F acute kidney injury when the sample is obtained.

13 . The method of claim 9 , wherein the sample is a urine sample, the assay result comprises a measured concentration of Chitinase-3-like protein 1, the subject is in RIFLE stage I or F acute kidney injury when the sample is obtained, the period is at least 72 hours long, and the period starts within 48 hours after the sample is obtained.

14 . A method of treating a subject for acute kidney injury, the method comprising:

performing an assay configured to detect Chitinase-3-like protein 1 in a body fluid sample obtained from the subject to provide an assay result, wherein assay results are combined using multivariate logistical regression, loglinear modeling, neural network analysis, n-of-m analysis, decision tree analysis, calculating ratios of markers, or a combination thereof;

correlating the assay result to a decreased likelihood of recovery from acute kidney injury to a maximum RIFLE stage of I or F over a period of at least 24 hours beginning within 7 days after the sample was obtained, by:

comparing the assay result to a threshold value obtained from a population study, wherein the threshold separates the population into a first subpopulation above the threshold and a second subpopulation at or below the threshold, the first subpopulation having a decreased likelihood of recovering from acute kidney injury relative to the second subpopulation, and

assigning the subject to the first subpopulation; and

treating the subject for non-recovery from acute kidney injury, wherein the treatment comprises renal replacement therapy, withdrawing delivery of compounds that are known to be damaging to the kidney, delaying procedures that are known to be damaging to the kidney, modifying diuretic administration, or administering one or more agents or measured volumes of fluid to restore normal fluid levels, electrolyte levels, or hemodynamics; and

wherein by correlating and comparing the assay results, the above method discriminates between persistent and non-persistent forms of acute kidney injury (AKI).

15 . The method of claim 14 , wherein the subject is in RIFLE stage F acute kidney injury when the sample is obtained.

16 . The method of claim 14 , wherein the decreased likelihood is of the subject recovering from acute kidney injury to a maximum RIFLE stage of R over the period of at least 24 hours.

17 . The method of claim 16 , wherein the subject is in RIFLE stage I or F acute kidney injury when the sample is obtained.

18 . The method of claim 14 , wherein the decreased likelihood is of the subject recovering from acute kidney injury to a maximum RIFLE stage of 0 over the period of at least 24 hours.

19 . The method of claim 18 , wherein the subject is in RIFLE stage R acute kidney injury when the sample is obtained.

20 . The method of claim 18 , wherein the subject is in RIFLE stage I or F acute kidney injury when the sample is obtained.