Analytic global OSCE ratings are sensitive to level of training

There are several reasons for using global ratings in addition to checklists for scoring objective structured clinical examination (OSCE) stations. However, there has been little evidence collected regarding the validity of these scales. This study assessed the construct validity of an analytic global rating with 4 component subscales: empathy, coherence, verbal and non-verbal expression.

A total of 19 Year 3 and 38 Year 4 clinical clerks were scored on content checklists and these global ratings during a 10-station OSCE. T-tests were used to assess differences between groups for overall checklist and global scores, and for each of the 4 subscales.

The mean global rating was significantly higher for senior clerks (75.5% versus 71.3%, t55 = 2.12, P < 0.05) and there were significant differences by level of training for the coherence (t55 = 3.33, P < 0.01) and verbal communication (t55 = 2.33, P < 0.05) subscales. Interstation reliability was 0.70 for the global rating and ranged from 0.58 to 0.65 for the subscales. Checklist reliability was 0.54.

In this study, a summated analytic global rating demonstrated construct validity, as did 2 of the 4 scales measuring specific traits. In addition, the analytic global rating showed substantially higher internal consistency than did the checklists, a finding consistent with that seen in previous studies cited in the literature. Global ratings are an important element of OSCE measurement and can have good psychometric properties. However, OSCE researchers should clearly describe the type of global ratings they use. Further research is needed to define the most effective global rating scales.