Calprotectin and neutrophil gelatinase–associated lipocalin in the differentiation of pre‐renal and intrinsic acute kidney injury

Abstract

Urinary calprotectin has recently been identified as a promising biomarker for the differentiation of pre-renal and intrinsic acute kidney injury (AKI). This study compares the diagnostic performance of calprotectin and neutrophil gelatinase-associated lipocalin (NGAL) in this differential diagnosis. Urinary calprotectin and NGAL concentrations were assessed in a study population of 87 subjects including 38 cases of intrinsic AKI, 24 cases of pre-renal AKI and 25 healthy controls. Urinary tract obstruction, renal transplantation and metastatic cancer were defined as exclusion criteria. Mean calprotectin concentrations were significantly lower in pre-renal (190.2±205.7ngmL(-1) ) than in intrinsic AKI (6250.1 ±7167.2ngmL(-1) , P<0.001). Receiver-operating characteristic (ROC) analysis provided an AUC of 0.99. Mean NGAL concentrations were significantly higher in intrinsic than in pre-renal AKI as well (458.1±695.3 vs. 64.8±62.1ngmL(-1) , P=0.001) providing an AUC of 0.82. A combination of the present study population with the cohort of the proof of concept study led to a population of 188 subjects (58 pre-renal AKI, 90 intrinsic AKI, 40 healthy controls). ROC analyses provided an AUC of 0.97 for calprotectin and 0.76 for NGAL yielding sensitivity and specificity values of 93.3 and 94.8% (calprotectin) vs. 75.3 and 72.4% (NGAL). Optimal cut-off values were 440ngmL(-1) (calprotectin) and 52ngmL(-1) (NGAL). Pyuria increased calprotectin concentrations independent of renal failure. This study shows that both calprotectin and NGAL are able to differentiate between pre-renal and intrinsic AKI after exclusion of pyuria. In the present population, calprotectin presents a higher sensitivity and specificity than NGAL.