Abstract
BACKGROUND: The reliability in Objective Structured Clinical Exams (OSCEs) is based on variance introduced due to examiners, stations, items, standardized patients (SP), and the interaction of one or more of these items with the candidates. The impact of SPs on the reliability has not been well studied. Accordingly, the main purpose of the present study was to assess the accuracy of portrayal by standardized patients. METHODS: Four stations from a ten station high-stakes OSCE were selected for video recording. Due to the large number of candidates to be evaluated, the OSCE was administered using four assessment tracks. Four SPs were trained for each case (n = 16). Two physician assessors were trained to assess the accuracy of SP portrayal using a station-specific instrument based on the station guidelines. For the items with disagreement a third physician was asked to review and the mode was used for analysis. Each instrument included case-specific items on verbal and physical portrayal using a 3-point rating scale ("yes", "yes, but" and "not done"). The physician assessors also scored each SP on their overall performance based on a 5-item anchored global rating scale ("very poor", "poor", "ok", "good", and "very good"). SPs at location 1 were trained by one trainer and SPs at location 2 had another trainer. All SPs were employed in a high-stakes OSCE for at least the second time. RESULTS: The reliability of rating scores ranged from Cronbach's alpha of .40 to .74. Verbal portrayal by SPs did not significantly differ for most items; however, the facial expressions of the SPs differed significantly (p < .05). An emergency management station that depended heavily on SPs physical presentation and facial expressions differed between all four SPs trained for that station. CONCLUSIONS: Variation of trained SP portrayal of the same station across different tracks and at different times in OSCE may contribute substantial error to OSCE assessments. The training of SPs should be strengthened and constantly monitored during the exam to ensure that the examinees' scores are a true reflection of their competency and devoid of exam errors.