doi: 10.1016/j.annemergmed.2025.10.014. Epub 2025 Dec 16. The Limit of Detection in the Emergency Department Trial (LEGEND): A Stepped-Wedge Cluster Randomized Trial to Rule Out Acute Myocardial Infarction and Reduce Hospital Length of Stay for Patients Presenting to the Emergency Department

Study objectives: The Limit of Detection in the Emergency Department (LEGEND) rule-out strategy integrates high-sensitivity cardiac troponin assay concentrations with shared decision making to rapidly assess emergency patients with suspected acute coronary syndrome (ACS). We hypothesized that the LEGEND rule-out strategy would reduce length of stay (LOS), increase the proportion of patients safely discharged within 4 hours, reduce cardiac testing, and decrease hospital representations, while maintaining patient safety.

Methods: We conducted a stepped-wedge cluster randomized controlled trial in 4 Australian emergency departments from August 2019 to July 2020. We included adult patients presenting with suspected ACS. We randomized sites to implement the LEGEND strategy. The primary outcome was LOS. Secondary outcomes included discharge from hospital within 4 hours, cardiovascular tests, representations, index, and 30-day events.

Results: The study included 9,944 patients, 5,347 in the standard care and 4,597 in the intervention arm. For patients in the LEGEND cohort (presentation troponin ≤2 ng/L), the mean LOS was 3.6 hours shorter in the intervention arm than the standard care arm (95% confidence interval [CI] 2.5 to 4.6 hours). The proportion of patients safely discharged within 4 hours increased by 22.9% (95% CI 19.5% to 26.3%), and cardiac testing decreased by 7.8% (95% CI 4.6% to 11.1%). There were no differences in representations, index events, or 30-day events.

Conclusion: The LEGEND rule-out strategy safely ruled out acute myocardial infarction, reduced hospital LOS, increased the proportion of patients discharged within 4 hours, and reduced cardiac testing.