Evaluating the predictive value of osteoarthritis diagnoses in an administrative database

Objective To assess the positive and negative predictive values of osteoarthritis (OA) diagnoses contained in an administrative database. Methods We identified all members (≥18 years of age) of a Massachusetts health maintenance organization with documentation of at least one health care encounter associated with an OA diagnosis during the period 1994–1996. From this population, we randomly selected 350 subjects. In addition, we randomly selected 250 enrollees (proportionally by the age and sex of the 350 subjects) who did not have a health care encounter associated with an OA diagnosis. Trained nurse reviewers ed OA‐related clinical, laboratory, and radiologic data from the medical records of both study groups (all but 1 chart was available for review). Pairs of physician reviewers evaluated the ed information for both groups of subjects and rated the evidence for the presence of OA according to 3 levels: definite, possible, and unlikely. Results Among the group of patients with an administrative diagnosis of OA, 215 (62%) were rated as having definite OA, 36 (10%) possible OA, and 98 (28%) unlikely OA, according to information contained in the medical record. The positive predictive value of an OA diagnosis was 62%. In those without an administrative OA diagnosis, 44 (18%) were assigned a rating of definite OA. The negative predictive value of the absence of an administrative OA diagnosis was 78%. Conclusion Use of administrative data in epidemiologic and health services research on OA may lead to both case misclassification and underascertainment.