Urinary liver‐type fatty acid‐binding protein as a prognostic marker in patients with acute heart failure

Aims Urinary liver‐type fatty acid‐binding protein (L‐FABP) is expressed in proximal tubular epithelial cells and excreted into the urine during tubular injury. We hypothesized that high urinary L‐FABP is associated with poor prognosis in patients with acute heart failure (AHF). Methods and results We analysed 623 patients (74 ± 13 years old; 60.0% male patients) with AHF. Urinary L‐FABP levels were measured at the time of admission and adjusted for the urinary creatinine concentration. The primary endpoint was all‐cause mortality. The median value and interquartile range of urinary L‐FABP levels were 6.66 and 3.37–21.1 μg/gCr, respectively. Urinary L‐FABP levels were significantly correlated with both beta‐2 microglobulin and cystatin C levels; the correlation with the former was higher than that with the latter. During the follow‐up of 631 (interquartile range: 387–875) days, 142 deaths occurred. A high tertile of urinary L‐FABP level was associated with high mortality; this association was retained after adjusting for other covariates (second tertile hazard ratio 1.40, P = 0.152 vs. first tertile; third tertile hazard ratio 1.94, P = 0.005 vs. first tertile). Conclusions Urinary L‐FABP is more closely associated with tubular dysfunction than with glomerular dysfunction. Tubular dysfunction, which was evaluated based on urinary L‐FABP levels, in patients with AHF is associated with all‐cause mortality and is independent of pre‐existing risk factors. L‐FABP should be considered for use in the prognosis of AHF.