Uniform or Sex-Specific Cardiac Troponin Thresholds to Rule Out Myocardial Infarction at Presentation

BACKGROUND Myocardial infarction can be ruled out in patients with a single cardiac troponin measurement. Whether use of a uniform rule-out threshold has resulted in sex-differences in care remains unclear. OBJECTIVES To evaluate implementation of a uniform rule-out threshold in females and males with possible myocardial infarction, and to derive and validate sex-specific thresholds. METHODS The implementation of a uniform rule-out threshold (<5 ng/L) with a high-sensitivity cardiac troponin I assay was evaluated in consecutive patients presenting with possible myocardial infarction. The proportion of low-risk patients discharged from Emergency Department (ED) and incidence of myocardial infarction or cardiac death at 30 days were determined. Sex-specific thresholds were derived and validated, and proportion of female and male patients stratified as low-risk compared with uniform threshold RESULTS: In 16,792 patients (58±17 years, 46% female) care was guided using a uniform threshold. This identified more female than male patients as low-risk (73% versus 62%), but a similar proportion of low-risk patients were discharged from ED (81% for both) with fewer than 5 (<0.1%) patients having a subsequent myocardial infarction or cardiac death at 30 days. Compared to uniform threshold of <5 ng/L, use of sex-specific thresholds would increase the proportion of female (61.8% versus 65.9%) and reduce the proportion of male (54.8% versus 47.8%) patients identified as low-risk. CONCLUSIONS Implementation of a uniform rule-out threshold for myocardial infarction was safe and effective in both sexes. Sex-specific rule-out thresholds should be considered, but their impact on effectiveness and safety may be limited.