Improved diagnostic performance of high‐sensitivity cardiac troponins in muscle dystrophies using comprehensive definition criteria for cardiac involvement: A longitudinal study on 35 patients

Background and purpose Sparse information is available on the correct interpretation of elevated high‐sensitivity cardiac troponin (hs‐cTn) in confirmed muscular dystrophies. Methods Serum concentrations of hs‐cTn T (hs‐cTnT) and hs‐cTn I (hs‐cTnI) were determined in 35 stable outpatients with confirmed skeletal muscle dystrophies. We calculated sensitivities, specificities, and positive and negative predictive values of hs‐cTnT and hs‐cTnI for identification of cardiac involvement using a comprehensive definition that included diastolic left ventricular and right ventricular function, strain analysis using two‐dimensional transthoracic echocardiogram and magnetic resonance imaging, myocardial biopsies, and consideration of a variety of triggers for cardiac injury, including arrhythmias, conduction disorders, and hypoxemia due to respiratory failure. Results Cardiac involvement was diagnosed in 34 of 35 cases. Specificities of hs‐cTnT increased from 12.5% to 100% (p = 0.0006) applying the comprehensive definition compared to a definition based on electrocardiography and echocardiography alone. At the recommended 99th percentile upper limit of normal, sensitivities were significantly lower for hs‐cTnI than for hs‐cTnT (29.4% vs. 100%, p = 0.0164). Conversely, the specificities of hs‐cTnT and hs‐cTnI increased to 100% when using the comprehensive definition criteria for diagnosing cardiac involvement. Conclusions Elevated hs‐cTnT but not hs‐cTnI discriminates cardiac involvement in cases with confirmed skeletal muscle dystrophies with very high sensitivity and 100% specificity. Prior reports on worse performance may be explained by the use of less sensitive imaging methods or incomplete assessment of cardiac involvement.