Neutrophil gelatinase-associated lipocalin is a sensitive biomarker for the early diagnosis of acute rejection after living-donor kidney transplantation

Early diagnosis of kidney allograft dysfunction is crucial for the management and long-term survival of transplanted kidneys. We investigated whether neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18), and liver-type fatty acid-binding protein (L-FABP) are capable of being used as novel biomarkers of acute kidney allograft dysfunction. We measured serum and urine NGAL, urine IL-18, and urine L-FABP levels on the first 3 days after transplantation. To assess the diagnostic sensitivity of these biomarkers, a receiver-operating characteristic curve (ROC) was plotted, and the area under the curve (AUC) was calculated to quantify the accuracy of the parameter. Sections from paraffin-embedded biopsy specimens were examined by immunohistochemistry for NGAL expression. Twelve cases were clinically diagnosed as acute rejection (AR) by renal biopsy. Urine NGAL was the most sensitive of these markers for detection of acute kidney allograft dysfunction. The cutoff value of urine NGAL was 66.0 ng/ml, with an AUC of 0.79 (95 % CI 0.68-0.88). Sensitivity of serum NGAL was about the same as urine NGAL with an AUC of 0.75 (0.64-0.85). IL-18 and L-FABP were 0.584 (95 % CI 0.433-0.725) and 0.612 (95 % CI 0.460-0.749), respectively. NGAL was more useful than other biomarkers to detect AR of kidney allograft dysfunction. NGAL staining intensity was significantly increased in the proximal tubules of the transplants with AR than in transplants that were not acutely rejected. Urine NGAL level was found to be the most sensitive biomarker of acute kidney allograft dysfunction after living-donor kidney transplantation.