Classification Criteria for Hand, Knee, and Hip Osteoarthritis (OA): Observations Based on an Australian Twin Registry Study of OA

ABSTRACT. Objective. The American College of Rheumatology (ACR) classification criteria for osteoarthritis (OA) permit the categorization of individuals for hand, knee, and hip OA and are of defined sensitivity and specificity. They depend on both clinical and radiographic aspects of ~A. The clinical diagnosis of OA in the peripheral skeleton is dependent on the skilled examination of several clinical features charac-teristic of the condition, while the interpretation of radiographs is a perceptual skill based on appreci-ating specific structural features on plain radiographs. We investigated the interrater reliability of the ACR classification criteria for OA when applied in a community based sample. Methods. The study was part of a multifaceted diagnostics protocol, evaluating methodologic issues, in the conduct of genetic research in OA. From a cohort of 118 pairs of twins registered with the Australian Twins Registry (ATR), standard clinical examinations of hands, knees, and hips were performed on 74 complete and 11 incomplete pairs of twins over age 50 years. The pairs were selected to represent both twin pairs who had previously self-reported a diagnosis of OA, as well as those who had not. Rheumatologists who performed the assessments were blind to the original self-report. All subjects were examined independently by one of 2 pairs (NB/AK or NBIKM) of consultant rheumatologists, blind to one another's assessments. Each rheumatologist separately assessed the hands, knees, and hips