Evaluating the validity evidence of an OSCE: results from a new medical school

To prevent the problems of traditional clinical evaluation, the "Objective Structured Clinical Examination (OSCE)" was presented by Harden as a more valid and reliable assessment instrument. However, an essential condition to guarantee a high-quality and effective OSCE is the assurance of evidence to support the validity of its scores. This study examines the psychometric properties of OSCE scores, with an emphasis on consequential and internal structure validity evidence.

Fifty-three first year medical students took part in a summative OSCE at the Lebanese American University-School of Medicine. Evidence to support consequential validity was gathered by using criterion-based standard setting methods. Internal structure validity evidence was gathered by examining various psychometric measures both at the station level and across the complete OSCE.

Compared to our actual method of computing results, the introduction of standard setting resulted in lower students' average grades and a higher cut score. Across stations, Cronbach's alpha was moderately low.

Gathering consequential and internal structure validity evidence by multiple metrics provides support for or against the quality of an OSCE. It is critical that this analysis be performed routinely on local iterations of given tests, and the results used to enhance the quality of assessment.