Objective To evaluate the impact of implementing a high sensitivity assay for cardiac troponin I on long term outcomes in patients with suspected acute coronary syndrome.
Design Secondary observational analysis of a stepped wedge, cluster randomised controlled trial.
Setting 10 secondary and tertiary care centres in Scotland, UK.
Participants 48 282 consecutive patients with suspected acute coronary syndrome. Myocardial injury was defined as any high sensitivity assay result for cardiac troponin I >99th centile of 16 ng/L in women and 34 ng/L in men.
Intervention Hospital sites were randomly allocated to either early (n=5 hospitals) or late (n=5 hospitals) implementation of a high sensitivity cardiac troponin I assay with sex specific diagnostic thresholds.
Main outcome measure The main outcome was myocardial infarction or death at five years.
Results 10 360 patients had cardiac troponin concentrations greater than the 99th centile, of whom 1771 (17.1%) were reclassified b