A resource efficient and reliable standard setting method for OSCEs: Borderline regression method using standardized patients as sole raters in clinical case encounters with medical students

Finding a reliable, practical and low-cost criterion-referenced standard setting method for performance-based assessments has proved challenging. The borderline regression method of standard setting for OSCEs has been shown to estimate reliable scores in studies using faculty as raters. Standardized patients (SPs) have been shown to be reliable OSCE raters but have not been evaluated as raters using this standard setting method. Our study sought to find whether SPs could be reliably used as sole raters in an OSCE of clinical encounters using the borderline regression standard setting method. SPs were trained for on a five-point global rating scale. In an OSCE for medical students, SPs completed skills checklists and the global rating scale. The borderline regression method was used to create case passing scores. We estimated the dependability of the final pass or fail decisions and the absolute dependability coefficients for global ratings, checklist scores, and case pass-score decisions using generalizability theory. The overall dependability estimate is 0.92 for pass or fail decisions for the complete OSCE. Dependability coefficients (0.70–0.86) of individual case passing scores range demonstrated high dependability. Based on our findings, the borderline regression method of standard setting can be used with SPs as sole raters in a medical student OSCE to produce a dependable passing score. For those already using SPs as raters, this can provide a practical criterion-referenced standard setting method for no additional cost or faculty time.