Background High-sensitivity troponin (hs-cTn) assays enable MI to be ruled out earlier, but the effectiveness and safety of this approach is uncertain. We compared a conventional pathway using the 99th centile and serial testing at presentation and at 6–12 hours, with a rapid rule out pathway that uses lower hs-cTn concentrations to risk stratify patients at presentation and earlier serial testing.

Method and results A 6-centre stepped-wedge, cluster RCT was completed, evaluating the efficacy/safety of implementation of a rapid rule out pathway using a hs-cTnI assay. Consecutive patients were identified, with suspected ACS who had a hs-cTnI concentration within the normal range at presentation in 3 phases. During the validation phase, patients were assessed using the standard care pathway with serial hs-cTnI testing at presentation and 6–12 hours. All centres were randomized in a stepped-wedge fashion to the novel pathway, where MI is ruled out if hs-cTnI is <5 ng/L at presentation or between 5 ng/L and the 99th centile with a change <3 ng/L at 3 hours. Sequential hypothesis testing evaluated the superiority of the novel pathway for a primary efficacy endpoint of length of stay, and non-inferiority for a primary safety endpoint of MI or cardiac death 30 days following discharge.

Conclusions From Nov 2014 to Dec 2016, 36,322 patients with suspected ACS and hs-cTnI concentrations <99th centile at presentation were identified. All patients were followed up for at least one year. Median lengths of stay and the proportion with MI or cardiac death 30 days following discharge before and after implementation of the pathway will be reported. Non-inferiority for the primary safety endpoint will be concluded if the upper limit of the one-sided 95% CI is below the non-inferiority margin of 0.5%. The proportion of patients discharged directly from ED and proportion with MI or cardiac death one year following discharge will be reported.