The accuracy of administrative data diagnoses of systemic autoimmune rheumatic diseases.

OBJECTIVE: 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.
METHODS: 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.
RESULTS: 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%.
CONCLUSION: 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.