The risks of thoroughness: Reliability and validity of global ratings and checklists in an OSCE

Objective: To compare checklists against global ratings for student performance on each station in an OSCE without the confounder of the global rating scorer having first filled in the checklist. Method: Subjects were 96 medical students completing their pre-clinical studies, who took an 8 station clinical OSCE. 39 students were assessed with detailed performance checklists; 57 students went through the same stations but were assessed using only a single global rating per station. A subset of 39 students were assessed by two independent raters. Results: Inter-rater and inter-station reliability of the global rating was the same as for the checklist. Correlation with a concurrent multiple choice test was similar for both formats. Conclusion: The global rating was found to be as reliable as more traditional checklist scoring. A discussion of the validity of checklist and global scores suggests that global ratings may be superior.