Urinary L-FABP and its combination with urinary NGAL in early diagnosis of acute kidney injury after cardiac surgery in adult patients.

Background/aim: The early detection of acute kidney injury (AKI) may be become possible by several promising early biomarkers which may facilitate the early detection, differentiation and prognosis prediction of AKI. In this study, we investigated the value of urinary liver-type fatty acid-binding protein (L-FABP), neutrophil gelatinase-associated lipocalin (NGAL) and their combination in predicting the occurrence and the severity of AKI following cardiac surgery.

Methods: We prospectively followed 109 patients undergoing open heart surgery and identified 26 that developed AKI, defined as an increase in serum creatinine of ≥0.3 mg/dl or ≥150% of baseline creatinine. Serum creatinine (SCr), urinary L-FABP, and NGAL corrected by urine creatinine were tested pre-operation, at 0 hour and 2 hours post-operation. Each marker was assessed at each time point between patients with and without AKI. Receiver operating characteristic (ROC) curves and area under curves (AUC) were used to evaluate the diagnostic accuracy of urinary L-FABP, NGAL and their combination for predicting AKI.

Results: Patients were aged 63.0 ± 11.3 years, 66.1% were male and baseline SCr was 70.5 ± 19.1 umol/L. Of 109 patients, 26(23.9%) developed AKI (AKIN stage I, II and III were 46.2%, 34.6% and 19.2% separately). The levels of urinary L-FABP and NGAL were significantly higher in AKI patients than non-AKI patients at 0 hour and 2 hours postoperative. AUCs for L-FABP was 0.844 (sensitivity (ST) 0.846, specificity (SP) 0.819, cut-off (CO) 2226.50 μg/g Ucr) at 0 hours and 0.832 at 2 hours (ST 0.808, SP 0.747, CO 673.09 μg/g Ucr) while 0.866 for NGAL at 0 hours (ST 0.769, SP 0.819, CO 131.12 μg/g Ucr) and 0.871 at 2 hours (ST 0.808, SP 0.831, CO 33.73 μg/g Ucr) to predict AKI occurrence. Using a combination of L-FABP and NGAL analyzed at the same timepoint as above, we were able to obtain an AUC of 0.911-0.927, p < 0.001. Similar AUCs of 0.81-0.87 were found to predict AKI stage II-III.

Conclusions: Urinary L-FABP and NGAL increased at an early stage after cardiac surgery. The combination of the two biomarkers enhanced the accuracy of the early detection of postoperative AKI after cardiac surgery before a rise in SCr.