||OBJECTIVE: Self-reported diagnoses of inflammatory arthritis are not accurate. The primary study aim was to ascertain self-reported diagnoses of rheumatoid arthritis (RA) and ankylosing spondylitis (AS) in the Norwegian population-based Nord-Trondelag Health Study (HUNT) using hospital case files. The secondary aim was to provide updated estimates of the prevalence and incidence of RA and AS. METHODS: All inhabitants >/= 20 years old from the county of Nord-Trondelag were invited. Data from 70,805 unique participants from HUNT2 (1995-1997) and HUNT3 (2006-2008) were included. For participants who self-reported RA or AS, case files from all 3 hospitals in the catchment area were evaluated using standardized diagnostic criteria. RESULTS: Of 2703 self-reported cases of RA, 19.1% were verified in hospital files. Of 1064 self-reported cases of AS, 15.8% were verified. Of 259 cases self-reporting both RA and AS, 8.1% had RA and 5.4% had AS. Overall, a self-report of 1 or both diagnoses could not be verified in 82.1%, including 22.8% with insufficient information or no case file. The prevalence of RA was 768 (95% CI 705-835) per 100,000. The incidence of RA from HUNT2 to HUNT3 was 0.48 (0.41-0.56) per 1000 per year. The prevalence of AS was 264 (228-305) per 100,000. The incidence of AS from HUNT2 to HUNT3 was 0.19 (0.15-0.24) per 1000 per year. CONCLUSION: Self-reported diagnoses of RA and AS are often false-positive. The prevalence and incidence of RA were comparable to reports from similar populations. The incidence of AS was higher than previously reported in a mixed population from Norway.
||V. Videm, MD, PhD, Professor, Department of Laboratory Medicine, Children's and Women's Health, NTNU, and Senior Consultant, Department of Immunology and Transfusion Medicine, St. Olavs Hospital; R. Thomas, MBBS, FRACP, MD, Professor, Translational Research Institute, University of Queensland; M.A. Brown, MBBS, MD, Director of Genomics, Queensland University of Technology, Institute of Health and Biomedical Research, Princess Alexandra Hospital; M. Hoff, MD, PhD, Associate Professor, Department of Public Health and General Practice and Department of Neuroscience, NTNU, and Senior Consultant, Department of Rheumatology, St. Olavs Hospital