Abstract Background Acute kidney injury (AKI) is commonplace after surgery and is correlated with a higher risk of morbidity, mortality and economic burden. Identifying early onset AKI is crucial in managing patients, improving outcomes thereby reducing economic burden to all. Creatinine is widely utilized for detecting AKI. However, its elevation is delayed post kidney injury. The biomarkers kidney injury molecule (KIM-1) and neutrophil gelatinase associated lipocalin (NGAL) have been evaluated as early AKI predictors with promising results. This prospective pilot study aims to address the data deficit by evaluating these biomarkers as early predictors of AKI in a subset of patients undergoing cardiopulmonary bypass (CPB) surgery. We theorize that NGAL and KIM-1 will be good markers of early AKI post cardiac surgery. Methods This study was conducted within a year at The University Hospital of the West Indies with 18 patients available for consent. Urine and serum samples were collected pre-operatively, 2 hrs, 4hrs and 24hrs post-surgery for evaluation. Urine KIM-1 and NGAL concentrations were determined using ELISA kits (Elabscience). Serum creatinine concentration was assessed on the Cobas analyzer. Independent sample t-tests and Pearsons’s chi-square tests were performed to analyze the biomarkers, peri-operative and demographic data obtained. ROC curves assessed the diagnostic performance of the biomarker tests and for those that were significant, a cutoff value for that biomarker was determined with its associated sensitivity and specificity. Statistical analyses were performed using SPSS version 28 Results Two patients died peri-operatively, while four patients developed AKI. Prolonged CPB and aortic cross clamped times were significant risk factors for developing AKI. AKI was associated with a longer hospital stay. NGAL was an excellent predictive biomarker for AKI 2hrs post-surgery where the AUC for receiver operating characteristics was 0.925, p=0.016, 95% CI with a sensitivity of 0.75 and specificity of 1.00, at a cut off value of 165.76 ng/ml. NGAL was also found to be useful in detecting AKI severity (defined by KDIGO guidelines 2012). There was an early rise in the mean serum creatinine level, from 94.75 µmol/L pre-operatively to146.75 µmol/L, 2hrs post operatively. The AUC for creatinine at 4hrs after surgery was 0.938, p=0.011 with a cutoff of 107.50µmol/L at a sensitivity of 1.000 and specificity 0.833. The AUC for creatinine at 24hrs was 0.958, p=0.008 with a sensitivity and specificity of 1.00 and 0.917 respectively, at a cutoff value of 120.50 µmol/L. KIM-1 was not statistically significant for detecting AKI. Conclusion This study demonstrated the need for a similar large-scale study and the potential of urine NGAL to be a superior predictive biomarker for detecting AKI at 2hrs after CPB surgery. Urine NGAL was useful in detecting the severity of AKI. KIM-1 was not statistically significant in predicting early AKI. Serum creatinine concentration increased early in AKI patients at 2hrs post-surgery and was excellent at discriminating AKI and non-AKI patients at 4hrs and 24hrs post-surgery. Recommendations to improve early diagnosis of AKI include testing NGAL at 2hrs after CPB surgery and serum creatinine early after surgery.
Mohansingh et al. (Wed,) studied this question.