Introduction: A primary aim of residency training is to develop competence in clinical reasoning. However, there are few instruments that can accurately, reliably, and efficiently assess residents’ clinical decision-making ability. This study aimed to externally validate the script concordance test in emergency medicine (SCT-EM), an assessment tool designed for this purpose.Methods: Using established methodology for the SCT-EM, we compared EM residents’ performance on the SCT-EM to an expert panel of emergency physicians at three urban academic centers. We performed adjusted pairwise t-tests to compare differences between all residents and attending physicians, as well as among resident postgraduate year (PGY) levels. We tested correlation between SCT-EM and Accreditation Council for Graduate Medical Education Milestone scores using Pearson’s correlation coefficients. Inter-item covariances for SCT items were calculated using Cronbach’s alpha statistic.Results: The SCT-EM was administered to 68 residents and 13 attendings. There was a significant difference in mean scores among all groups (mean + standard deviation: PGY-1 59 + 7; PGY-2 62 + 6; PGY-3 60 + 8; PGY-4 61 + 8; 73 + 8 for attendings, p < 0.01). Post hoc pairwise comparisons demonstrated that significant difference in mean scores only occurred between each PGY level and the attendings (p < 0.01 for PGY-1 to PGY-4 vs attending group). Performance on the SCT-EM and EM Milestones was not significantly correlated (r = 0.12, p = 0.35). Internal reliability of the exam was determined using Cronbach’s alpha, which was 0.67 for all examinees, and 0.89 in the expert-only group.Conclusion: The SCT-EM has limited utility in reliably assessing clinical reasoning among EM residents. Although the SCT-EM was able to differentiate clinical reasoning ability between residents and expert faculty, it did not between PGY levels, or correlate with Milestones scores. Furthermore, several limitations threaten the validity of the SCT-EM, suggesting further study is needed in more diverse settings
