Background/Purpose:  Ankylosing spondylitis (AS) is associated with extra-articular manifestations (EAMs) such as acute anterior uveitis (AAU), inflammatory bowel disease (IBD), and psoriasis. Little is known about the characteristics of patients who develop any EAM. We aimed to identify characteristics associated with the development of EAMs in a prevalence cohort of patients with AS.

Methods:  Twelve year follow-up data from patients included in the Outcome in AS International Study (OASIS) were used. Additionally, medical charts were checked for the presence of AAU, IBD or psoriasis, by two independent extractors. Baseline demographic, clinical and radiographic characteristics of patients with and without uveitis, IBD or psoriasis were compared. Logistic regression was performed to identify characteristics associated with the presence of any EAM. Furthermore, Cox regression and survival analyses were performed to identify characteristics associated with development of any EAM over time. Analysis were performed with baseline characteristics as well as with time-varying characteristics.

Results:  216 patients were included (mean age 43.6 years (SD 12.7), 154 (71%) men, mean symptom duration 20.5 years (SD 11.7), 174 (85%) HLA-B27 positive and mean follow-up period 8.3 years (SD 4.3)). At baseline, 59 (27%) patients had any EAM, of which 39 (18%) AAU, 15 (7%) IBD, and 9 (4%) psoriasis. Four patients (2%) had more than one EAM. At baseline, patients with AAU compared with patients without AAU were older (49.1 vs 42.4 years, p<0.01), had a longer symptom duration (25.9 vs 19.3 years, p<0.01), and more radiographic damage (modified Stoke AS Spinal Score 16.9 vs 10.6, p=0.03). Patients with psoriasis compared with patients without psoriasis were older (51.3 vs 43.3 years, p=0.05). There were no differences between patients with and without IBD. During follow-up 27 patients developed a new EAM; 19 AAU, 9 IBD, and 5 psoriasis with incidence rates of 0.9%, 0.4%, and 0.02% per year, respectively. The following time-varying characteristics were associated with the development of IBD in univariable analysis: AS Disease Activity Score (HR 2.81, 95%-CI 1.43-5.53), Bath Ankylosing Disease Activity Index (HR 1.47 95%-CI 1.09-1.98), C-reactive protein (HR 1.02, 95%-CI 1.00-1.05) Bath AS Functional index (HR 1.40, 95%-CI 1.09-1.80) and Bath AS Global Score (HR 1.46, 95%-CI 1.10-1.96). CRP was also weakly associated with the development of AAU (HR 1.02, 95%-CI 1.01-1.04) in time-varying analysis. No significant associations with development of psoriasis were found.

Conclusion:  At baseline, a substantial number of patients already had an EAM in this prevalence cohort with relatively long symptom duration. Development of new EAMs was infrequently observed. In particular disease activity, but also physical function and patient global assessment, were associated with development of IBD. CRP was associated with the development of AAU. Characteristics associated with the development of psoriasis were not found.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/disease-activity-is-associated-with-development-of-inflammatory-bowel-disease-in-ankylosing-spondylitis-12-year-results-from-oasis/