Using borderline methods to compare passing standards for OSCEs at graduation across three medical schools

Abstract

Medical schools in the UK set their own graduating examinations and pass marks. In a previous study we examined the equivalence of passing standards using the Angoff standard-setting method. To address the limitation this imposed on that work, we undertook further research using a standard-setting method specifically designed for objective structured clinical examinations (OSCEs). Six OSCE stations were incorporated into the graduating examinations of 3 of the medical schools that took part in the previous study. The borderline group method (BGM) or borderline regression method (BRM) was used to derive the pass marks for all stations in the OSCE. We compared passing standards at the 3 schools. We also compared the results within the schools with their previously generated Angoff pass marks. The pass marks derived using the BGM or BRM were consistent across 2 of the 3 schools, whereas the third school generated pass marks which were (with a single exception) much lower. Within-school comparisons of pass marks revealed that in 2 schools the pass marks generally did not significantly differ using either method, but for 1 school the Angoff mark was consistently and significantly lower than the BRM. The pass marks set using the BGM or BRM were more consistent across 2 of the 3 medical schools than pass marks set using the Angoff method. However, 1 medical school set significantly different pass marks from the other 2 schools. Although this study is small, we conclude that passing standards at different medical schools cannot be guaranteed to be equivalent.