Urinary biomarkers for early detection of recovery in patients with acute kidney injury

Abstract

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.

Keywords: Acute Kidney Injury; Biological Markers; Cystatin C; Neutrophil Gelatinase-Associated Lipocalin.

Fig. 1

BUN (A), plasma Cr (B), urine NGAL (C), urine NGAL/Cr (D), urine cystatin C (E), urine cystatin C/Cr (F) levels every 2 days for 8 day period stratified by recovery and non-recovery from AKI. Urine NGAL level shows statistically significant difference between groups since day 0 preceding the difference in plasma Cr level.^*P < 0.01 comparing recovery group vs non-recovery group; ^†P < 0.05 comparing recovery group vs non-recovery group. BUN, blood urea nitrogen; Cr, creatinine; NGAL, Neutrophil gelatinase-associated lipocalin; AKI, acute kidney injury.

Fig. 2

ROC curve for the detection of AKI recovery using urine NGAL at day 0 after AKI diagnosis. ROC curve demonstrates the prognostic sensitivity and specificity of urine NGAL in the prediction of AKI recovery (AUC = 0.78; 95% CI 0.64-0.90). AUC, Area under the curve; ROC, Receiver operating characteristic; AKI, Acute kidney injury; NGAL, Neutrophil gelatinase-associated lipocalin.