Evaluation of a Methodologic Approach to Define an Inception Cohort of Rheumatoid Arthritis Patients Using Administrative Data.

Abstract

Identifying incident rheumatoid arthritis (RA) is desirable in order to create inception cohorts. We evaluated an approach to identify incident RA in health plan claims data. Both Medicare and commercial claims data were linked to Corrona, a US RA registry. We evaluated the accuracy of year of RA onset in the registry (gold standard) versus different claims algorithms, varying International Classification of Diseases, Ninth Revision codes for RA/arthritis, duration of health plan enrollment preceding diagnosis (minimum of 1 versus 2 years), and use of RA medications. Results were reported as positive predictive values (PPVs) of the claims-based algorithm for incident RA. Depending on the algorithm tested and whether patients were enrolled in Medicare or the commercial health plan, the PPVs for incident RA ranged from 68-81%. A 2-year clean period free of all RA-related diagnoses and medications was somewhat more optimal although, by comparison, a 1-year clean period yielded similar PPVs and retained approximately 90% more RA patients for analysis. Claims-based algorithms can accurately identify incident RA.