Urinary Neutrophil Gelatinase-Associated Lipocalin: A Potential Biomarker for Predicting Rapid Progression of Drug-Induced Chronic Tubulointerstitial Nephritis

IntroductionThe role of urinary biomarkers of kidney injury in the prediction of adverse clinical outcomes in drug-induced chronic tubulointerstitial nephritis (D-CTIN) has not been well described.MethodsA total of 36 patients with D-CTIN were enrolled in the study. The baseline urinary excretion of neutrophil gelatinase-associated lipocalin (NGAL), α1-microglobin (α1-MG), albumin (mAlb) and total protein were measured, and estimated glomerular filtration rate change rates within a period of 6 to 33 (mean: 24 months) follow-up months were recorded.ResultsAreas under the receiver-operator characteristic curve of urinary NGAL, α1-MG, mAlb and total protein for predicting deterioration of estimated glomerular filtration rate were 0.707, 0.631, 0.685 and 0.678, respectively. The cutoff points that maximized the combined sensitivity and specificity for NGAL, α1-MG, mAlb and total protein were 37.71 ng/mL, 33.20 μg/mL, 6.91 mg/L and 60.00 mg/L, respectively. At these thresholds, the sensitivity and specificity was 64.7% and 78.9% for NGAL, 66.7% and 50.0% for α1-MG, 80.0% and 50.0% for mAlb and 70.6% and 63.2% for total protein, respectively. The median renal survival time (years) of patients with urinary NGAL level exceeding 37.705 ng/mL was shorter than that of patients with urinary NGAL level below 37.705 ng/mL (1.59 ± 0.79 versus 2.09 ± 0.63, P = 0.040, χ² = 4.218).ConclusionsIncrease of baseline urinary NGAL was better than α1-MG, mAlb and total protein in predicting renal function deterioration in patients with D-CTIN. This noninvasive approach has potential to serve as a practical tool in D-CTIN prognosis.