Urinary Biomarkers for Early Detection of Recovery in Patients with Acute Kidney Injury

Urinary biomarkers of acute kidney injury (AKI) have been revealed recently to be useful for prior prediction of AKI. However, it is unclear whether these urinary biomarkers can also detect recovery from established AKI. Urinary biomarkers, including neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C, were measured every 2 days for 8 days in 66 patients with AKI. At day 0, there were no significant differences in plasma creatinine, BUN, and urine cystatin C between AKI patients in the recovery (n = 33) and non-recovery (n = 33) groups. Plasma creatinine concentrations were significantly lower in the recovery group (3.0 ± 2.0 mg/dL) than in the non-recovery group (5.4 ± 1.9 mg/dL) on day 4 after AKI diagnosis (P < 0.001). In contrast, there were significant differences in urine NGAL between the two groups starting on day 0 (297.2 ± 201.4 vs 407.6 ± 190.4 ng/mL, P = 0.025) through the end of the study (123.7 ± 119.0 vs 434.3 ± 121.5 ng/mL, P < 0.001). The multiple logistic regression analysis showed that urine NGAL could independently predict recovery from AKI. Conclusively, this prospective observational study demonstrates that urine NGAL can be a highly versatile marker for early detection of the recovery phase in established AKI patients.