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 (R) DxC 600 Synchron (R) 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 (r(s) = 0.33, p = 0.001). Conclusion: The study demonstrated that level S 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.