Development of a clinical prediction rule for diagnosing hip osteoarthritis in individuals with unilateral hip pain

STUDY DESIGN: Prospective cohort/predictive validity study. OBJECTIVE: To determine the diagnostic accuracy of common clinical examination items and to construct a preliminary clinical prediction rule for diagnosing hip osteoarthritis (OA) in individuals with unilateral hip pain. BACKGROUND: The current gold standard for the diagnosis of hip OA is a standing anteroposterior (AP) radiograph of the pelvis, Other than for Altman's criteria, little research has been done to determine the accuracy of clinical examination findings for diagnosing hip OA. METHODS AND MEASURES: Seventy-two subjects completed the study. Each subject received a standardized history, physical examination, and standing AP radiograph of the pelvis. Subjects with a Kellgren and Lawrence score of 2 or higher based on the radiographs were considered to have definitive hip OA. Likelihood ratios (LRs) were computed to determine which clinical examination findings were most diagnostic of hip OA. Potential predictor variables were entered into a logistic regression model to determine the most accurate set of clinical examination items for diagnosing hip OA. RESULTS: Twenty-one (29%) of the 72 subjects had radiographic evidence of hip OA. A clinical prediction rule consisting of 5 examination variables was identified. If at least 4 of 5 variables were present, the positive LR was equal to 24.3 (95% confidence interval: 4.4-142.1), increasing the probability of hip OA to 91%. CONCLUSION: The preliminary clinical prediction rule provides the ability to a priori identify patients with hip pain who are likely to have hip OA. A validation study should be done before the rule can be implemented in routine clinical practice.