Urinary liver‐type fatty acid‐binding protein is independently associated with graft failure in outpatient kidney transplant recipients

Urinary liver‐type fatty acid‐binding protein (uL‐FABP) is a biomarker of kidney hypoxia and ischemia, and thus offers a novel approach to identify early kidney insults associated with increased risk of graft failure in outpatient kidney transplant recipients (KTR). We investigated whether uL‐FABP is associated with graft failure and whether it improves risk prediction. We studied a cohort of 638 outpatient KTR with a functional graft ≥1‐year. During a median follow‐up of 5.3 years, 80 KTR developed graft failure. uL‐FABP (median 2.11, interquartile range 0.93–7.37 µg/24"/>h) was prospectively associated with the risk of graft failure (hazard ratio 1.75; 95% confidence interval 1.27–2.41 per 1‐SD increment; P = .001), independent of potential confounders including estimated glomerular filtration rate and proteinuria. uL‐FABP showed excellent discrimination ability for graft failure (c‐statistic of 0.83) and its addition to a prediction model composed by established clinical predictors of graft failure significantly improved the c‐statistic to 0.89 (P for F‐test <.001). These results were robust to several sensitivity analyses. Further validation studies are warranted to evaluate the potential use of a risk‐prediction model including uL‐FABP to improve identification of outpatient KTR at high risk of graft failure in clinical care.