Urinary Liver-type Fatty Acid-Binding Protein Predicts Residual Renal Function Decline in Peritoneal Dialysis Patients

BACKGROUND Liver-type fatty acid-binding protein (L-FABP) is a predictive marker for the early detection of acute kidney injury; however, less is known about how useful it is for predicting residual renal function (RRF) decline in patients on peritoneal dialysis (PD). MATERIAL AND METHODS The study subjects were 35 patients on PD who underwent multiple peritoneal equilibration tests (PETs) between October 2011 and October 2019. Urinary L-FABP levels were analyzed with enzyme-linked immunosorbent assay. The relationship between baseline clinical data, including urinary L-FABP levels and the subsequent annual rate of renal Kt/V decline, was investigated. RESULTS The median follow-up duration was 11 months and the rate of renal Kt/V decline was 0.29/y. Compared with outcomes in the group with renal Kt/V preservation, renal Kt/V decline was associated with both high daily levels of urinary protein excretion (0.60 g/d [range, 0.50-0.87] vs. 0.36 g/d [range, 0.19-0.48]; P=0.01) and high daily levels of urinary L-FABP excretion (111.2 mg/d [range, 76.1-188.6] vs. 61.5 mg/d [range, 35.7-96.0]; P=0.002). Multiple logistic regression analysis showed that only high daily levels of urinary L-FABP excretion were independently associated with renal Kt/V decline (odds ratio 1.03, 95% confidence interval 1.00-1.05; P=0.001). Furthermore, higher daily levels of urinary L-FABP excretion were significantly correlated with the higher annual rate of renal Kt/V decline (r=0.71, P<0.001). CONCLUSIONS We demonstrated that daily levels of urinary L-FABP are associated with RRF decline in patients on PD. The results of the present study indicate that assessment of urinary L-FABP levels may help predict RRF decline in patients on PD.