ABSTRACT
PURPOSE: Cardiac troponin (cTn) is the gold standard biomarker for assessing cardiac damage. Previous studies have demonstrated increases in plasma cTn because of extreme exercise, including marathon running. We developed an easy-to-use, ultrasensitive assay for cardiac troponin I (cTnI) by combining single-molecule counting (SMC™) technology with dried blood spot (DBS) collection techniques and validated the assay on a cohort of marathon runners by correlating postmarathon cTnI elevations with training or risk variables. METHODS: An SMC-DBS method was developed for accurate and reproducible measurement of cTnI in fingerstick whole blood. Samples were collected from 42 runners both before and immediately after running a marathon. A similar collection was obtained from 22 non-running control individuals. Pre- and postrace questionnaires containing health and training variables were correlated with cTnI concentration. RESULTS: The assay quantified cTnI in all controls and marathon runners, both before and after the race. Prerace concentrations were significantly higher in marathon runners vs controls (median 3.1 vs 0.4 pg/mL; P < 0.0001). Immediate postmarathon concentrations were increased in 98% of runners (median elevation, 40.5 pg/mL; P < 0.001), including many above traditional cutoffs for acute myocardial infarction. Several health and training variables trended toward significant correlation with cTnI elevations. CONCLUSION: While further studies are needed to better understand the mechanisms and clinical implications of exercise-induced cTnI elevations, the present study suggests several variables that may be associated with such elevations and demonstrates a simple, cost-effective method for monitoring cTnI during exercise, managing chronic disease, and/or for assessing risk in large populations.
