Inflammatory bowel disease in axial spondyloarthritis patients. Is there any specific clinical picture? Data from the RESPONDIA and REGISPONSER registries.

BACKGROUND

Inflammatory bowel disease (IBD) affects 5%-10% of ankylosing spondylitis (AS) patients. Prior data suggest AS patients with IBD may have more severe disease and lower HLA-B27 prevalence. Yet, little is known about potential distinctions in AS with IBD compared to those without IBD.

OBJECTIVE

To investigate the clinical characteristics and radiographic differences between patients with (AS) with and without concurrent IBD.

DESIGN

This multicenter, observational, cross-sectional study included patients meeting European Spondyloarthropathy Study Group criteria from the Registry of Spondyloarthritis of Spanish Rheumatology (REGISPONSER) and Ibero-American Registry of Spondyloarthropathies (RESPONDIA) registries.

METHODS

Characteristics and disease burden were compared between patients with and without IBD. Multivariate logistic regression identified factors independently associated with IBD presence in patients with AS.

RESULTS

We included a total of 2766 patients with AS (1254 from REGISPONSER and 1512 from RESPONDIA), among whom 142 patients (5.13%) presented with concomitant IBD. AS patients with concurrent IBD were less frequently male, had a lower prevalence of HLA-B27 positivity, experienced a lower prolonged diagnostic delay, had a lower frequency of enthesitis, and received more commonly intensified treatment compared to those without IBD. In terms of structural damage, the Bath Ankylosing Spondylitis Radiology Index (BASRI) score for the sacroiliac joints (SIJs), cervical spine, and lumbar spine was lower in patients with AS and IBD than in those without IBD. In the multivariable analysis, the presence of IBD was significantly associated with a lower prevalence of HLA-B27 and enthesitis, with odds ratios (OR) of 0.32 (95% confidence interval (CI): 0.20-0.52) and 0.58 (95% CI: 0.33-0.97), respectively. Furthermore, structural damage in SIJs (BASRI) was significantly decreased in patients with IBD, with an OR of 0.79 (95% CI: 0.64-0.99).

CONCLUSION

The presence of IBD in AS is associated with lower HLA-B27 positivity, less enthesitis, and less radiographic damage in this large population study.