The impact of age on the diagnosis of type 1 myocardial infarction using high-sensitivity cardiac troponin

Abstract

Abstract Background Cardiac troponin concentrations are influenced by age and comorbidities with values above the 99th centile diagnostic threshold more common in older patients without myocardial infarction. Despite this, rule-in thresholds for myocardial infarction are applied universally regardless of age or comorbidities. Purpose We sought to evaluate how age and cardiovascular comorbidities influence the diagnostic performance of high-sensitivity cardiac troponin I for myocardial infarction. Methods In a secondary analysis of a multi-centre randomised controlled trial, we identified 45,991 consecutive patients with suspected acute coronary syndrome without ST-segment elevation myocardial infarction. The diagnostic performance of high-sensitivity cardiac troponin I measured at presentation for type 1 myocardial infarction was evaluated for the sex-specific 99th centile and thresholds three and five times this value in patients stratified by age (under 50 years, between 50 and 75 years, and over 75 years). The effect of comorbidities on diagnostic accuracy was evaluated using regression modelling. Results Of the 45,991 patients, 8,187 (18%) had myocardial injury of which 7,677 (94%) had a presentation troponin above the sex-specific 99th centile. Mean age of those with myocardial injury was 74 years (range 18–108). The positive predictive value (PPV) of the 99th centile was 54.6% (95% confidence interval [CI] 50.6–58.8%), 58.8% (56.9–60.6%) and 36.6% (35.1–38.2%) in patients under 50 years, between 50 and 75 years, and over 75 years, respectively. Rule-in thresholds three and five-times the 99th centile gave a higher PPV in all age groups with a PPV of 45.5% (43.1–47.8%) and 50.4% (47.6–53.2%), respectively in those aged over 75 years (Table 1). Regardless of threshold, specificity and PPV was lowest in patients over 75 years and decreased with advancing age (Figure 1). Across all age groups, the presence of heart failure resulted in the greatest decrease in PPV (36.9% [34.6–39.2%] versus 50.6% [49.3–51.8%]). Adjusting for cardiovascular comorbidities resulted in modest change in the discrimination of cardiac troponin for myocardial infarction (area under curve 0.89 vs 0.90) and did not prevent a decline in diagnostic accuracy in older patients. Conclusion The specificity and PPV of high-sensitivity cardiac troponin I for myocardial infarction decreases with advancing age. Cardiovascular comorbidities impact the PPV of troponin, but do not explain the decline in diagnostic accuracy with age. Clinicians should be aware of these important differences in performance by age of the diagnostic and rule-in thresholds for myocardial infarction when interpreting troponin results in older patients. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): University of Edinburgh Figure 1