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

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. Descriptive study. Department of Chemical Pathology and Endocrinology, AFIP in collaboration with AFIC/ NIHD, Rawalpindi, from April to December 2011. 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. 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 [Cl] 0.83 - 0.96] with sensitivity of 90.9% [95% Cl 58.7 - 98.5] and specificity of 98.7% [95% Cl 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 [r[s] = 0.33, p = 0.001]. The study demonstrated that levels of urine NGAL in patients suffering from AKI increased significantly at 4 has compared to serum creatinine levels. Urine NGAL is an early predictive biomarker of AKI after CPB