Diagnostic errors affect patient safety and lead to high costs. Cognitive bias is a key source of diagnostic error, and the framing effect poses a particular clinical challenge. The extent to which individual factors affect susceptibility to the framing bias is unclear, and the role of expertise in particular is contested across the literature.

This study investigated the effects of framing bias on diagnostic reasoning among medical students. We hypothesised that the effects attributable to framing would be mediated by the number of years of medical education completed.

Participants were randomly assigned on an automated basis with allocation concealment to complete one of the two case vignettes consistent with pulmonary embolism (PE). The two versions contained objectively identical clinical data but varied semantically and ordinally to create differences in frame; one emphasised features consistent with PE, while the other did not. After evaluating the vignette, participants provided their top three differential diagnoses.

183 medical students (MS) completed the study (101 MS2, 42 MS3 and 40 MS4), of whom 29.5% identified PE as a diagnosis of interest. The likelihood of identifying PE differed based on the frame to which participants were exposed (p

Our results suggest that cognitive frame influences diagnostic reasoning, and that its effects may be mediated by years of medical education completed. These findings inform future targeted initiatives in undergraduate medical education.