Rapid detection of acute kidney injury by urinary neutrophil gelatinase-associated lipocalin after cardiopulmonary bypass surgery.

OBJECTIVE: To determine the accuracy of neutrophil gelatinase-associated lipocalin (NGAL) in early detection of acute kidney injury (AKI) after cardiopulmonary bypass (CPB) surgery by comparing with serum creatinine.

STUDY DESIGN: Descriptive study.

PLACE AND DURATION OF STUDY: Department of Chemical Pathology and Endocrinology, AFIP in collaboration with AFIC/ NIHD, Rawalpindi, from April to December 2011.

METHODOLOGY: Eighty eight patients undergoing CPB surgery in AFIC/NIHD were included by consecutive sampling. Blood samples of subjects for serum creatinine analysis were drawn pre-operatively, 4 h, 24 h and 48 h after CPB surgery. Spot urine samples for NGAL were collected at 4 h after CPB surgery. Urine samples were analyzed on Abbott ARCHITECT i2000SR analyzer whereas serum creatinine samples were measured on Beckman UniCel® DxC 600 Synchron® Clinical System.

RESULTS: Out of 88 patients, 11 (13%) cases developed AKI 4 h postoperatively. Urinary NGAL increased markedly at 4 h postoperatively as compared to serum creatinine which showed rise at 24 - 48 h after cardiac surgery. Analysis of urine NGAL at a cutoff value of 87 ng/ml showed area under the curve of 0.91 [95% confidence interval (CI) 0.83 - 0.96] with sensitivity of 90.9% (95% CI 58.7 - 98.5) and specificity of 98.7% (95% CI 92.9-99.8). There was a positive correlation of 4 h urine NGAL and serum delta creatinine at 48 h, which was statistically significant (rs = 0.33, p = 0.001).

CONCLUSION: The study demonstrated that levels of urine NGAL in patients suffering from AKI increased significantly at 4 h as compared to serum creatinine levels. Urine NGAL is an early predictive biomarker of AKI after CPB.