Point‐of‐care cTnI Tests Accurately Predict Heat Stroke Severity; Proof of Concept for a Heat Stroke Field Test

Abstract

Heat stroke (HS) remains a significant health threat for both civilians and the U.S. Armed Forces. Despite the substantial public health concern posed by HS, there is still no field or clinical test of HS severity. We suggested previously that cardiac troponin (cTnI) could serve as a robust biomarker of HS severity. In the current study, we hypothesized that cTnI band intensity on a small, portable, Lifesign MI© point‐of‐care strip (POC strip) could be used to predict overall HS severity and HS induced organ damage. In brief, conscious male rats (N=24) continuously monitored for HR, BP, and core temperature (Tc) (radiotelemetry) were taken to a TcMax of 41.9 ± 0.1°C and then allowed to recover for 24h at Ta of 20°C. Blood samples (~120µL) were taken at Tc,Max and 24hrs‐post heat via submandibular bleed and 4 drops of blood were placed on POC strips. POC cTnI band intensity was ranked using a simple 4 point scale via 2 blinded scorers, and then compared to cTnI levels measured by a clinical grade blood analyzer (iSTAT®). Blood was also analyzed for biomarkers of systemic organ damage (VetScan® Liver Profile). HS severity, as previously defined using in‐heat heart rate & blood pressure as well as 24‐h recovery Tc profile, correlated strongly with cTnI (r= 0.82) & markers of systemic organ damage (albumin r= 0.90, alanine aminotransferase r= 0.87, blood urea nitrogen r= 0.71). POC cTnI band intensity ranking accurately predicted cTnI levels (r= 0.80) and overall HS severity (r = 0.91). This suggests that qualitative cTnI POC tests can accurately determine HS severity and could serve as simple, portable, cost effective HS tests in the field. Author views not official US Army or DoD policy.