False-Positive Troponins: Clinical Misclassification, Delayed Recognition, and Health Care Costs in a Real-World Cohort.

BACKGROUND: Cardiac troponin immunoassays are critical for diagnosing myocardial infarction. Up to 10% of elevated results may be falsely positive because of heterophile antibodies or macrotroponin complexes, leading to misdiagnoses. METHOD: We conducted a retrospective cohort study at the Royal Melbourne Hospital, Australia (January 2021-December 2024). The Abbott high-sensitivity troponin-I assay was the primary assay used in standard practice. Interference was confirmed according to institutional protocol when alternative assays (Ortho Vitros or Roche high-sensitivity assays) performed on the same plasma sample were negative. Clinical characteristics, investigations, treatment, documentation, and health care costs were reviewed. RESULTS: Among 148,987 high-sensitivity troponin-I requests, 38 patients underwent alternate testing. In the 26 patients with confirmed interference, the median age was 48 years (interquartile range 36-60), with equal sex distribution; 39% had no cardiovascular risk factors. The median troponin levels were 150 ng/L. All underwent transthoracic echocardiography, and 73% received coronary imaging (computed tomography or invasive angiography). More than half had normal cardiac findings. Misdiagnoses included myocarditis (35%) and non-ST-elevation myocardial infarction (23%); 81% received treatment changes, including colchicine, aspirin, or anticoagulation. The median delay to recognition was 7.5 months. Documentation was inconsistent: only 54% had interference recorded in the medical record and 19% in discharge summaries. Estimated costs averaged AUD $16,331 per patient, largely because of avoidable admissions and procedures. CONCLUSIONS: Troponin assay interference is an under-recognised source of false-positive troponin elevations, leading to diagnostic error, unnecessary testing, and substantial health care costs. Prompt recognition, consistent documentation, and routine confirmatory testing using alternate assays are essential to mitigate clinical and economic consequences.