Probing the effect of OSCE checklist length on inter-observer reliability and observer accuracy.

Purpose: The Objective Structured Clinical Examination (OSCE) is a widely employed tool for measuring clinical competence. In the drive toward comprehensive assessment, OSCE stations and checklists may become increasingly complex. The objective of this study was to probe inter-observer reliability and observer accuracy as a function of OSCE checklist length.

Method: Study participants included emergency physicians and senior residents in Emergency Medicine at Dalhousie University. Participants watched an identical series of four, scripted, standardized videos enacting 10-min OSCE stations and completed corresponding assessment checklists. Each participating observer was provided with a random combination of two 40-item and two 20-item checklists. A panel of physicians scored the scenarios through repeated video review to determine the 'gold standard' checklist scores.

Results: Fifty-seven observers completed 228 assessment checklists. Mean observer accuracy ranged from 73 to 93% (14.6-18.7/20), with an overall accuracy of 86% (17.2/20), and inter-rater reliability range of 58-78%. After controlling for station and individual variation, no effect was observed regarding the number of checklist items on overall accuracy (p=0.2305). Consistency in ratings was calculated using intraclass correlation coefficient and demonstrated no significant difference in consistency between the 20- and 40-item checklists (ranged from 0.432 to 0.781, p-values from 0.56 to 0.73).

Conclusions: The addition of 20 checklist items to a core list of 20 items in an OSCE assessment checklist does not appear to impact observer accuracy or inter-rater reliability.