Liver fatty acid-binding protein point-of-care testing detects heat-induced organ damage: a pilot study in Japanese male self-defense force personnel

Heat-related illnesses cause multiple organ injuries, including acute kidney injury (AKI). Recent studies have reported that heat-induced AKI can progress to chronic kidney disease (CKD). We previously reported that urinary levels of liver fatty acid-binding protein (L-FABP) are elevated in patients with severe heat-related illness. In this study, we prospectively examined the detection ability of L-FABP rapid assay kit (L-FABP Point-of-Care [POC] kit) for heat-induced organ damage in prehospital settings. After applying the exclusion criteria, 65 Japanese male military personnel who intended to carry out training in a hot environment were analyzed. The L-FABP POC kit enabled the detection of heat-induced kidney and/or liver damage after heat exposure (defined as serum creatinine [Cr] ≥ 1.2 mg/dL and total bilirubin ≥ 1.2 mg/dL) with a high negative predictive value (95.7%). L-FABP-positive participants showed higher serum Cr and total bilirubin levels than L-FABP-negative participants. Moreover, L-FABP-positive participants showed higher acyl-to-free carnitine ratios, indicating carnitine insufficiency which leads to impaired fatty acid oxidation, as well as high and rapid elevation of their core temperature in comparison to L-FABP-negative participants. In conclusion, the L-FABP POC kit may be useful as a screening tool for detecting heat-induced organ damage, which would prevent prolonged organ dysfunction.