Evaluating the predictive value of osteoarthritis diagnoses in an administrative database

Objective. To assess the positive and negative predictive values of osteoar thritis (OA) diagnoses contained in an administrative database. Methods. We identified all members (greater than or equal to 18 years of ag e) 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 subjec ts, In addition, we randomly selected 250 enrollees (proportionally by the age and seg of the 350 subjects) who did not have a health care encounter a ssociated with an OA diagnosis. Trained nurse reviewers abstracted OA-relat ed clinical, laboratory, and radiologic data from the medical records of bo th study groups (all but 1 chart was available for review). Pairs of physic ian reviewers evaluated the abstracted information for both groups of subje cts and rated the evidence for the presence of OA according to 3 levels: de finite, 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 withou t an administrative OA diagnosis, 44 (18%) were assigned a rating of defini te 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 underascertainm ent.