Cardiac Troponin Thresholds in Children and Young Adults: A Multi-Center Cohort Study.

BACKGROUND: The role of high-sensitivity cardiac troponin (cTn) assays for children and young adults is uncertain, and no guidance is available on diagnostic thresholds. This study evaluates the effect of applying pediatric compared to adult upper reference limits (URLs) for cTn. METHODS: We carried out a retrospective multicenter international cohort study of consecutive children and young adults (1 day to 18 years) undergoing cTn I or T testing at 4 tertiary care hospitals in Norway and Scotland, United Kingdom, from 2013 to 2023. Myocardial injury was classified using the adult sex-specific 99th percentile URL, a pediatric sex-specific 99th percentile, and a pediatric sex-specific 97.5th percentile. Diagnoses of myocarditis were obtained from the Norwegian Patient Register and the Scottish Morbidity Record. RESULTS: In total, 9833 (46.6% female) children and young adults underwent cTn testing. Applying the adult sex-specific 99th percentile, 1771 (18.0% [95% CI, 17.3%-18.8%]) had myocardial injury compared with 1762 (17.9% [95% CI, 17.2%-18.7%]) using a pediatric 99th percentile. In contrast, applying a pediatric sex-specific 97.5th percentile would identify 2261 (23.0% [95% CI, 22.2%-23.8%]) with myocardial injury (a 28% relative increase). Infants had a higher frequency of myocardial injury than those 1-18 years old (1035/1104; 93.8% [95% CI, 92.2%-95.1%] vs 1226/8729; 14.0% [95% CI, 13.3%-14.8%] using pediatric sex-specific 97.5th percentile, P < 0.001). Testing for cTn increased over the study period (τ = 0.42, P < 0.001). CONCLUSIONS: The use of pediatric-specific 97.5th percentile URLs for cTn would increase classification of myocardial injury in children and young adults. The clinical implications of this are uncertain and require further study given cTn testing has increased over the last decade.