Samples were immediately refrigerated and then centrifuged at 5000 g for 10 minutes at 4 C within 4 hours of collection. Samples were stored in separated, 1 mL aliquots without additives at 80 C till biomarker measurements. Urine YKL 40 levels were assessed in the last quarter of 2012 using enzyme linked immunosorbent assay may kits as previously described. Population based urine levels have not been defined for YKL 40, but published data for 22 non diabetic patients with normal renal function indicate urine YKL 40 is typ ically undetectable or less than 0. 2 ng ml in healthy indi viduals. Urine NGAL levels were measured via ELISA by the Devarajan laboratory between 2008 and 2009 as reported in our prior publication. Population mean levels of urine NGAL in healthy adults are between 10 23 ng ml.

Note, the documented intra assay and inter assay coefficients of variation for both YKL 40 and NGAL ELISA methods are less than 10%. All laboratory measurements were performed by personnel blinded to patient information. Statistical analysis Our previously described baseline clinical model for predicting risk of the primary outcome included the following variables, age 65 years, body mass index, male gender, non White race, baseline GFR, diabetes, hyper tension and surgery before AKI. We used a predefined cutoff of 5 ng ml for all analyses based on the median urine YKL 40 value for recipients with immediate graft function in previously published results from our kidney transplant cohort.

We used multivariate logistic re pared median urine levels for both YKL 40 and NGAL based on the presence or absence of key baseline clinical characteristics using Mann Whitney U tests. All analyses were performed with SAS version 9. 3 for Windows. A Type I error of 0. 05 was considered statistically significant for all analyses. Results Cohort description and YKL 40 measurements A total of 284 hospitalized patients with AKI were en rolled in the study, and after exclusions, 249 were available for analysis. Seventy two patients developed the primary outcome. Baseline charac teristics are summarized in Table 1. Median urine levels for both YKL 40 and NGAL separated by these baseline characteristics are provided in Table 2. The median value for urine YKL 40 was 0. 2 ng ml. Our prior study demonstrated that recipients with the most rapid improvement in renal function immediately after kidney transplant had median urinary YKL 40 levels of 5 ng ml. Eighty eight percent of the current cohort had urinary levels below 5 ng ml, and of those, 69% were adjudi cated as pre renal. In contrast, only 42% of those with YKL 40 5 ng ml were classified as pre renal. Of the 31 patients with YKL 40 5 ng ml, 16 had the primary outcome compared to Volasertib mw 56 218 of those with YKL 40 5 ng ml.