Background: High sensitivity troponin I (Hs troponin I) is a precise and sensitive marker of myocardial injury. However, interferences by antibodies are not uncommon in immunoassays. Macrotroponin is one such phenomenon, in which immune complexes are formed between troponin and circulating antibodies, giving rise to false-positive results. Case Presentation: This is a case of a 30-year-old male with elevated high sensitivity troponin I results of 419 ng/l (99th percentile upper reference limit for males is 34.2 ng/l). The test was performed on Abbott Alinity i immunoassay analyzer (Abbott Gmbh & Co. KG, Wiesbaden, Germany). Electrocardiogram, exercise tolerance test, and echocardiogram were all unremarkable. The results of creatinine kinase-myocardial component, troponin T, and conventional troponin I on VITROS ECi Immunodiagnostics System (Ortho-Clinical Diagnostics, Rochester, NY) were within normal limits. Laboratory experiments were carried out to evaluate the case, and the investigations conducted indicated the presence of macrotroponins in the specimen, which demonstrated cross immunoreactivity with the Alinity (Abbott) assay but not with the VITROS (Ortho) assay. Conclusion: Clinicians and laboratorians should be aware of the possible interference by macrotroponin in their assays and should be alerted when there is a discordance between the laboratory and clinical findings.

Keywords: Macrotroponin, cardiac biomarkers, autoantibody, heterophile antibody, immunoassay interferences, case report