Using standardized patients to measure professional performance of physicians.

To determine the nature of inaccuracies likely to occur when standardized patients (SPs) are used to measure physician behaviour and to evaluate the potential impact of these inaccuracies on estimates of physician performance. Secondary analysis from a randomized controlled trial. Family physicians' offices. Eighteen individuals, each portraying one of two patient scenarios, made a total of 179 visits to 92 family physicians who were participating in a separate randomized controlled trial to evaluate the impact of an educational workshop on implementation of preventive guidelines. Accuracy of SPs' portrayal of the assigned scenarios and accuracy of their coding of physician performance, determined on the basis of audiotapes of the visits and correlated with indicators of physicians' preventive practices. Accuracy of portrayal of the patient scenario was 84.8% for the male SPs and 93.5% for the female SPs. Inaccuracies in portrayal had no impact on physician performance scores. Accuracy of coding of physician performance was 90.5% for the female SPs (kappa = 0.66) and 90.1% for the male SPs (kappa = 0.68). Coding inaccuracies occurred most frequently for assessment of alcohol consumption and advice against smoking. SPs can provide valid information about physicians' professional performance. However, standardization of their activities must not be taken for granted. It may be more difficult to obtain standardized coding for counselling activities, an aspect of physician visits for which SPs are particularly appropriate.