Urine liver-type fatty acid-binding protein predicts graft outcome up to 2 years after kidney transplantation

Background Several new biomarkers for the detection of early tubular injury have been investigated in kidney transplant recipients. We recently identified day 2 urinary neutrophil gelatinase-associated lipocalin (NGAL) as a predictor of slow graft function and adverse 1-year outcome. In the present study, we further investigated the value of urinary NGAL and liver-type fatty acid binding protein (L-FABP) for predicting long-term graft outcomes up to 2 years. Methods This study was a single-center, prospective observational study. Serial urinary NGAL and L-FABP levels at 0 hours, 2 days, and 6 days after kidney transplantation (KT) were measured, and the clinical data were assessed during the 2-year period after KT. Results During the 2-year follow-up period, 13 (18.8%), 5 (7.2%), and 4 (5.8%) patients were diagnosed with acute T-cell-mediated rejection, acute antibody-mediated rejection (AMR) and chronic AMR, respectively. In addition, 10 patients (14.3%) developed calcineurin inhibitor toxicity and 6 (8.7%) developed BK viremia. The mean estimated glomerular filtration rates (eGFR) at 1 and 2 years after KT were 65.1 ± 19.1 and 58.5 ± 22.6 mL/min/1.73 m², respectively, When poor long-term graft function was defined as eGFR of less than 50 mL/min/1.73 m ² at 2 years, elderly donors, acute rejection, and high 0-hour urinary L-FABP levels were significant risk factors. Furthermore, in rejection-free patients, L-FABP was strongly associated with poor long-term graft function (P =.006). Multivariate logistic regression analysis showed that high 0-hour L-FABP (P =.015) and acute rejection (P =.006) were independent factors predicting poor long-term graft function. Receiver operating characteristic analysis showed that the area under the curve for urinary L-FABP was 0.692 (P =.036). Conclusions Our results suggest that urinary L-FABP may be a useful predictor of adverse long-term outcomes in KT patients.