Background Association between ankylosing spondylitis (AS) and inflammatory bowel disease (IBD) is well established. Some reports have suggested increased concomitance of rheumatoid arthritis (RA) with IBD, as well.
Objectives To examine the prevalence of IBD among incident patients with RA and AS in Finland
Methods Finland has a general sickness insurance covering the entire population. Patients with certain chronic diseases (e.g., RA, AS IBD, etc.) are entitled to special reimbursement of medications if their condition meets defined criteria. The reimbursement decisions are recorded in the national registry of the Social Insurance Institution. From this registry all incident cases of RA (ICD-10 code M05 for RF/anti-CCP positive and M06 for seronegative RA) and AS (ICD-10 code M45) between 1 Jan 2004 and 31 Dec 2007 were identified. From the same source prevalent cases of IBD (colitis ulcerosa, morbus Crohn; ICD-10 codes K50 and K51) were gathered and any coexistence recorded.
Results A total of 7209 incident patients over 17 years of age with RA (68% female, 65% RF positive, age 57±15) and 1436 with AS (40% female, age 38±11) were identified. Of the patients with RA, 35 individuals (0.49%; 95% CI: 0.34 to 0.67), 24 (0.49%) female and 11 (0.47%) male, already had IBD at the index day of reimbursement decision for antirheumatic medication. Age-adjusted rate ratio (RR) of women compared to men was 1.04 (95% CI: 0.50 to 2.19). Compared to the general population, the age and sex–adjusted standardized rate ratio (SRR) was 0.74 (95% CI: 0.51 to 1.03); for RF positive patients it was 0.69 (0.43 to 1.05) and for RF negative ones 0.83 (0.45 to 1.39).
Of the incident patients with AS, 29 individuals (2.0%; 95% CI: 1.4 to 2.9), 11 (1.93%) female and 18 male (2.08%), had concomitant IBD. Age-adjusted rate ratio (RR) of women compared to men was 1.07 (95% CI: 0.51 to 2.26). Age-and sex-adjusted SRR was 2.73 (1.83 to 3.92).
Conclusions Co-occurrence of incident RA with IBD was not increased compared to the general population.
Disclosure of Interest None declared
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