To examine the validity of case definitions for systemic autoimmune rheumatic diseases [SARD; systemic lupus erythematosus (SLE), systemic sclerosis (SSc), myositis, Sjögren's syndrome, vasculitis, and polymyalgia rheumatica] based on administrative data, compared to rheumatology records.
A list of rheumatic disease diagnoses was generated from population-based administrative billing and hospitalization databases. Subjects who had been seen by an arthritis center rheumatologist were identified, and the medical records reviewed.
We found that 844 Nova Scotia residents had a diagnosis of one of the rheumatic diseases of interest, based on administrative data, and had had = 1 rheumatology assessment at a provincial arthritis center. Charts were available on 824 subjects, some of whom had been identified in the administrative database with > 1 diagnosis. Thus a total of 1136 diagnoses were available for verification against clinical records. Of the 824 subjects, 680 (83%) had their administrative database diagnoses confirmed on chart review. The majority of subjects who were "false-positive" for a given rheumatic disease on administrative data had a true diagnosis of a similar rheumatic disease. Most sensitivity estimates for specific administrative data-based case definitions were > 90%, although for SSc, the sensitivity was 80.5%. The specificity estimates were also > 90%, except for SLE, where the specificity was 72.5%.
Although health administrative data may be a valid resource, there are potential problems regarding the specificity and sensitivity of case definitions, which should be kept in mind for future studies.