Objectives: To compare enteropathic spondylitis (ES) with psoriatic spondylitis (PS) and ankylosing spondylitis (AS), in patients on biological disease-modifying anti-rheumatic drug (bDMARD) treatment.
Methods: Patients who were enrolled in the HUR-BIO registry were included. ES patients were considered as the main study group; AS and PS patients were included as the control groups. ES was defined as patients with inflammatory bowel disease (IBD) having inflammatory back pain/spine symptoms plus radiological sacroiliitis.
Results: Sixty-four ES patients (46.9% female), 128 AS patients (39.1% female), and 92 PS patients (62% female) were analysed. Baseline erythrocyte sedimentation rate (ESR) was significantly higher in the ES group than in the AS group. Both the baseline ESR and C-reactive protein were also higher in the ES group compared with the PS group. Among the first bDMARD use, infliximab use was higher in the ES group than the other groups. There was a marginal significant difference between the SpA subgroups in the retention rates of the first bDMARDs (log-rank, p=0.059). Ulcerative colitis was a significant predictor for switching of bDMARDs in comparison to Crohn's disease. Regarding the treatment responses, no significant differences were relevant for the three groups in terms of 50% improvement of the initial Bath Ankylosing Spondylitis Disease Activity Index score, the Assessment of Spondyloarthritis International Society partial remission score, and 20% improvement of ASAS score.
Conclusions: A large majority of enteropathic spondyloarthritis patients on bDMARD treatment had radiographic sacroiliitis. ES patients had distinctive features that distinguish them from AS and PS patients.