Formative assessment of practical skills with peer-assessors: quality features of an OSCE in general medicine at the Heidelberg Medical Faculty

Background: Objective Structured Clinical Examinations (OSCEs) have become an established examination format at German medical faculties. Medical experts routinely use a summative assessment to evaluate practical and communicative skills, while the use of the OSCE format by student examiners, as a formative examination, remains rather limited. Objective: The formative OSCE program of the Department of General Practice and Implementation Research at the Heidelberg Medical Faculty, which is conducted and evaluated by peer tutors, is examined with regard to its quality criteria and compared with summative OSCEs from other departments. Methods: Difficulties and discriminatory power of individual testing stations were determined for the summative, as well as the formative OSCE, and compared with each other. To assess the reliability of the measurements, an analysis of the data was carried out using the Generalizability theory. In addition, a comparison is made between the assessments of student examiners and second assessments by medical experts. Results: The stations of the formative OSCE show similar difficulties as those of the summative comparison OSCEs (P(form)=0.882; P(sum)=0.845 – 0.902). With respect to measurement reliability, there are no differences between the OSCE in General Medicine and the other subjects. The assessments of student examiners and medical experts correlate highly (r=0.888). Conclusion: The formative OSCE in General Medicine is comparable to the summative comparison formats in terms of its quality criteria. The use of student examiners can be a reliable alternative to medical experts in formative OSCEs.