Cardiac troponin interferents in diagnosis and clinical management of myocarditis: a single center experience.

Background: Cardiac troponin (cTn) is a key myocardial injury biomarker; however, false-positive cTn results can occur due to heterophile antibodies and troponin macrocomplexes. We aimed to explore the potential confounding role of cTn interferents in patients with previous myocarditis. Methods: We retrospectively included myocarditis patients tested for cTn interferents due to suspicion of falsepositive cTn results because of long-standing, low-level plateau cTn and no or atypical symptoms, unremarkable ECG and normal coronary arteries. cTnI and cTnT concentrations were measured using fully-automated chemiluminescent two-site immunoassays. Results: During the study period (2005-2024), a total of 1143 patients with myocarditis were followed at our institution; of these, 29 (2.5 %) underwent cTn assay interference testing (20 male, median age 45 years, Q1-Q3, 33-53) due to suspected false-positive cTn results; 31 % (9/29) were interferent-positive. Among interferentpositive cases, troponin levels at the time of interferent testing were lower than at diagnosis (150 vs. 776 ng/ L, p = 0.018), and in 8/9 cases, identifying cTn interferents helped rule out suspected myocarditis relapse. In 25 % (5/20) of true cTn-positive cases without interferents, testing for interferents alone influenced treatment decisions and indications for invasive procedures. Conclusions: In our retrospective cohort study, cTn interferents were identified in approximately one-third of selected myocarditis patients with discordant clinical and biochemical findings, influencing management in nearly half of the cases. These findings highlight the potential clinical value of selective interferent testing and provide a basis for future prospective studies aimed at defining its optimal role in routine practice.