Impact of switching high-sensitivity cardiac troponin assays by sex in patients with suspected acute coronary syndrome: an interrupted time series analysis

Background Cardiac troponin concentrations are lower in females than males and sex-specific 99th percentile upper reference limits (URLs) are recommended to identify myocardial injury. Whether the impact of using a sex-specific URL to guide care is similar for cardiac troponin I and T assays is uncertain. Purpose To evaluate the impact of switching from a cardiac troponin I to a T assay with sex-specific URLs on management and outcomes in females and males with suspected acute coronary syndrome (ACS). Methods In a prospective interrupted time series study, consecutive patients with suspected ACS across three acute care hospitals were identified between October 2020 and October 2022. All sites changed from a high-sensitivity cardiac troponin I to a high-sensitivity cardiac troponin T assay using the manufacturer’s recommended sex-specific URLs in October 2021. In a pre-specified secondary analysis, the impact of sex on clinical outcomes was evaluated using generalised linear models that included interaction with the intervention. The primary outcome was hospital admission, and secondary outcomes included serial troponin testing, coronary angiography, and subsequent myocardial infarction, heart failure hospitalisation, or cardiovascular death at 1 year. Results Among 25,849 patients, 6,185 (median 59 [IQR 48-75] years) and 5,878 (61 [48-75] years) females, and 6,961 (59 [46-72] years) and 6,825 (59 [45-72] years) males, presented before and after the switch to cardiac troponin T. This increased the proportion identified with myocardial injury in both female (odds ratio [OR] 3.12, 95% confidence interval [CI] 2.26-4.31, P<0.001) and male (OR 2.18, 95% CI 1.61-2.97, P<0.001) patients (Figure 1A), but greater in females (Psex:intervention=0.006). Switching was associated with a similar increase in hospital admission in both females (OR 2.38, 95% CI 1.74-3.27, P<0.001) and males (OR 2.14, 95% CI 1.60-2.85, P<0.001; Figure 1B). After the switch, serial troponin testing increased (females: OR 5.34, 95% CI 3.90-7.33, P<0.001; males: OR 6.89, 95% CI 5.09-9.36, P<0.001; Figure 1C), but it was less in females (Psex:intervention<0.001). Compared to males, females were less likely to be admitted (OR 0.81, 95% CI 0.77-0.85, P<0.001) or to undergo coronary angiography (OR 0.43, 95% CI 0.39-0.48, P<0.001), and were at lower risk of subsequent myocardial infarction, heart failure hospitalisation, or cardiovascular death at 1 year (OR 0.68, 95% CI 0.60-0.77, P<0.001; Figure 1D), which was not influenced by assay. Conclusions Switching from a cardiac troponin I to a T assay with sex-specific thresholds increased the identification of myocardial injury in both sexes, but the increase was greater in females. Irrespective of the assay used, female patients with suspected acute coronary syndrome were less likely than males to be admitted to hospital for further investigation, but were also at lower risk of cardiovascular events.