Who will pass the dental OSCE? Comparison of the Angoff and the borderline regression standard setting methods.

Aim: Aim of this study is to elucidate which standard setting method is optimal to prevent incompetent students to pass and competent students to fail a dental Objective Structured Clinical Examination (OSCE).

Material And Methods: An OSCE with 14 test stations was used to assess the performance of 119 third year dental students in a training group practice. To establish the pass/fail standard per station, three standard setting methods were applied: the Angoff I method, the modified Angoff II with reality check and the Borderline Regression (BR) method. For the final decision about passing or failing the complete OSCE, three methods were compared: total compensatory (TC), a partial compensatory (PC) within clusters of competence and a non-compensatory (NC) model. The reliability of the pass/fail standard of the three methods was indicated by the root mean square error (RMSE). As a criterion measure, a sample of the students (n = 89) was rated in the clinic by their instructors and accordingly these students were divided into two groups: competent and incompetent students. The students' clinical rating (considered for this study as 'true qualification') was compared with the pass-fail classification resulting from the OSCE. Undeserved passing of an incompetent student was considered as more damaging than failing a competent student.

Results: The BR method showed more acceptable results than the two Angoff methods. In terms of pass rate the BR method showed the highest pass rates: for the TC model the Angoff method I and II and the BR showed pass rates of 86.6%, 86.6% and 97.5% respectively. For the PC model the pass rates were 30.3%, 34.5% and 61.3%, and for the NC model the pass rates were 0.8%, 1.7% and 7.6%. The BR method showed lower RMSEs (higher reliability): for the TC model the RMSEs were 1.3%, 1.0% and 0.3% for the Angoff I, Angoff II and BR method respectively, and for the PC model the RMSE of the clusters of competence range was 2.0-3.7% for Angoffs I; 1.8-2.2% for Angoff II and 0.6-0.7% for the BR method. In terms of incorrect decisions, the BR method had a higher loss due to incorrect decisions for the TC model than for the PC model which is in accordance with the results of other studies in medical education.

Conclusions: Therefore we conclude that the BR method in a PC model provides defensible pass/fail standards and seems to be the optimal choice for OSCEs in health education.