Abstract
OBJECTIVE: We examined hospitalizations for patients with known rheumatoid arthritis (RA) or giant cell arteritis (GCA) to evaluate whether hospitalization-related diagnoses accurately identified patients with rheumatologic diseases. METHODS: Diagnosis codes for hospitalizations in 1996-2012 among previously identified population-based cohorts of patients with RA or GCA were examined for RA or GCA mentions. RESULTS: RA or GCA mention occurred in only 55% of 2407 hospitalizations among patients with RA and 31% of 502 hospitalizations among patients with GCA. RA or GCA was mentioned more often in recent years, younger patients, and rheumatic medication users. CONCLUSION: Coding for RA or GCA during hospitalizations was often missed. Research using hospital diagnoses alone could be biased.