AbstractObjectiveTo determine the effectiveness of risk stratification using the Global Registry of Acute Coronary Events (GRACE) risk score (GRS) for patients presenting to hospital with suspected non-ST elevation acute coronary syndrome.DesignParallel group cluster randomised controlled trial.SettingPatients presenting with suspected non-ST elevation acute coronary syndrome to 42 hospitals in England between 9 March 2017 and 30 December 2019.ParticipantsPatients aged ≥18 years with a minimum follow-up of 12 months.InterventionHospitals were randomised (1:1) to patient management by standard care or according to the GRS and associated guidelines.Main outcome measuresPrimary outcome measures were use of guideline recommended management and time to the composite of cardiovascular death, non-fatal myocardial infarction, new onset heart failure hospital admission, and readmission for cardiovascular event. Secondary measures included the duration of hospital stay, EQ-5D-5L (five domain, five level version of the EuroQoL index), and the composite endpoint components.Results3050 participants (1440 GRS, 1610 standard care) were recruited in 38 UK clusters (20 GRS, 18 standard care). The mean age was 65.7 years (standard deviation 12), 69% were male, and the mean baseline GRACE scores were 119.5 (standard deviation 31.4) and 125.7 (34.4) for GRS and standard care, respectively. The uptake of guideline recommended processes was 77.3% for GRS and 75.3% for standard care (odds ratio 1.16, 95% confidence interval 0.70 to 1.92, P=0.56). The time to the first composite cardiac event was not significantly improved by the GRS (hazard ratio 0.89, 95% confidence interval 0.68 to 1.16, P=0.37). Baseline adjusted EQ-5D-5L utility at 12 months (difference −0.01, 95% confidence interval −0.06 to 0.04) and the duration of hospital admission within 12 months (mean 11.2 days, standard deviation 18 daysv11.8 days, 19 days) were similar for GRS and standard care.ConclusionsIn adults presenting to hospital with suspected non-ST elevation acute coronary syndrome, the GRS did not improve adherence to guideline recommended management or reduce cardiovascular events at 12 months.Trial registrationISRCTN 29731761