Background Axial spondyloarthritis (axSpA) is a common chronic inflammatory disease with predominantly axial symptoms. Besides axial symptoms, the disease is characterized by peripheral (arthritis, enthesitis, dactylitis), and extra-articular (uveitis, psoriasis, inflammatory bowel disease (IBD)) disease manifestations. A much debated question is whether the radiographic form (defined as ankylosing spondylitis or AS) and the non-radiographic form (nr-axSpA) of axSpA represent subsets of the same disorder or if they are distinct disease entities (1–4). Hypothesizing that AS and nr-axSpA reflect subsets of a single disease entity and have similar disease burden, we performed a meta-analysis of published studies of axial SpA in order to assess if the prevalence of peripheral and extra-articular disease manifestations is similar in AS and nr-axSpA.

Objectives The objective of this meta-analysis was to assess the prevalence of peripheral and extra-articular disease manifestations in AS and nr-axSpA.

Methods We performed a systematic literature search to identify publications describing the prevalence of peripheral and extra-articular disease manifestations in patients with AS and nr-axSpA. We assessed the risk of bias, between-study heterogeneity and extracted data. Pooled prevalence and prevalence differences were calculated.

Results Eight studies including 2236 AS patients and 1242 nr-axSpA patients were included. Seven out of 8 studies were longitudinal cohort studies. There was a male dominance in AS (70.4%; 95% CI 64.4–76.0%) but not in nr-axSpA (46.8%; 95% CI 41.7–51.9), which was independent from HLA-B27 prevalence. HLA-B27 prevalence was similar in AS (78.0%; 95% CI 73.9–81.9%) and nr-axSpA (77.4%; 95% CI 68.9–84.9%). The pooled prevalence of arthritis (29.7% (95% CI 22.4–37.4%) versus 27.9% (95% CI 16.0–41.6%)), enthesitis (30.4% (95% CI 3.7–65.8%) versus 34.1% (95% CI 4.7–71.0%)), dactylitis (6.0% (95% CI 4.7–7.5%) versus 6.0% (95% CI 1.9–12.0%)), psoriasis (10.2% (95% CI 7.5–13.2%) versus 10.9% (95% CI 9.1–13.0%)) and IBD (4.1% (95% CI 2.3–6.5%) versus 6.4% (95% CI 3.6–9.7%)) were similar in AS and nr-axSpA. The pooled uveitis prevalence was higher in AS (23.0% (95% CI 19.2–27.1%)) than in nr-axSpA (15.9% (95% CI 11.8–20.4%)).

Conclusions Peripheral and extra-articular manifestations are equally prevalent in AS and nr-axSpA, except for uveitis, which is slightly more prevalent in AS. These data support the concept that AS and nr-axSpA belong to one pathogenic entity with similar disease manifestations.

1. Wallis D, et al. Ankylosing spondylitis and nonradiographic axial spondyloarthritis: part of a common spectrum or distinct diseases? J Rheumatol 2013;40:2038–41.

2. Rudwaleit M, Khan MA, Sieper J. Commentary: The challenge of diagnosis and classification in early ankylosing spondylitis: Do we need new criteria? Arthritis Rheum 2005;52:1000–1008.

3. Robinson PC, et al. Axial spondyloarthritis: a new disease entity, not necessarily early ankylosing spondylitis. Ann Rheum Dis 2013;72:162–4.

4. Kiltz U, et al. Do patients with non-radiographic axial spondylarthritis differ from patients with ankylosing spondylitis? Arthritis Care Res 2012;64:1415–22.

Disclosure of Interest None declared