BackgroundPeripheral disease (arthritis, enthesitis and dactylitis) and extra-articular disease (uveitis, psoriasis and inflammatory bowel disease) is common in ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nr-axSpA). So far, however, summary data on the prevalence are lacking. The objective of this meta-analysis was to assess the prevalence of peripheral and extra-articular manifestations in ankylosing spondylitis (AS) and nr-axSpA.MethodsWe 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 and between-study heterogeneity, and extracted data. Pooled prevalence and prevalence differences were calculated.ResultsEight studies comprising 2236 patients with AS and 1242 with nr-axSpA were included: 7 of the studies were longitudinal cohort studies. There was male predominance 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 of the prevalence of human leukocyte antigen (HLA)-B27. The prevalence of HLA-B27 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 (28.8 % (95 % CI 2.6, 64.8) versus 35.4 % (95 % CI 6.1, 71.2)). 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 inflammatory bowel disease (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 prevalence of uveitis was higher in AS (23.0 % (95 % CI 19.2, 27.1 %)) than in nr-axSpA (15.9 % (95 % CI 11.8, 20.4 %)).ConclusionPeripheral and extra-articular manifestations are equally prevalent in AS and nr-axSpA, except for uveitis, which is slightly more prevalent in AS. These data provide evidence for the largely equal nature of disease manifestations in nr-axSpA and AS.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-016-1093-z) contains supplementary material, which is available to authorized users.

BackgroundAnti-CD74 IgG antibodies are reported to be elevated in patients with axial spondyloarthritis (axSpA). This study assessed the diagnostic value of anti-CD74 antibodies in patients with early axSpA.MethodsAnti-CD74 IgG and IgA antibodies were first measured in an exploratory cohort of patients with radiographic axSpA (138 patients with ankylosing spondyloarthritis (AS)) and 57 healthy controls and then were measured in patients with early axSpA (n = 274) and with non-SpA chronic back pain (CBP) (n = 319), participating in the spondyloarthritis caught early (SPACE) prospective cohort study of patients under 45 years old with early back pain (for ≥ 3 months, but ≤ 2 years).ResultsIn the exploratory cohort, anti-CD74 IgG antibodies were present in 79.7% of patients with AS vs. 43.9% of healthy controls (p < 0.001). Anti-CD74 IgA antibodies were present in 28.5% of patients with AS vs. 5.3% of healthy controls (p < 0.001). In the SPACE cohort, anti-CD74 IgG antibody levels were present in 46.4% of the patients with axSpA vs. 47.9% of the patients with CBP (p = 0.71). Anti-CD74 IgA antibodies were present in 54.7% of the patients with axSpA and 37.0% of the patients with CBP (p < 0.001). This resulted in a positive predictive value of 58.8% (compared to a prior probability of 46.2%) and a negative predictive value of 59.1% (compared to a prior probability of 53.8%). In a regression model, total serum IgA was associated with axSpA odds ratio (OR) 1.19, p < 0.001) whereas anti-CD74 IgA was not (OR) 1.01, p = 0.33). Furthermore, anti-CD74 IgA was associated with sacroiliitis on magnetic resonance imaging (MRI) (OR) = 2.50, p = 0.005) and heel enthesitis (OR) = 2.56, p = 0.002).ConclusionsAlbeit anti-CD74 IgA is elevated in patients with early axSpA, this elevation is not sufficiently specific to yield significant diagnostic value in patients under 45 years old presenting with early back pain.

ObjectiveSpondyloarthritis (SpA) can encompass axial, peripheral and extra-articular disease manifestations. Patients are classified as axial or peripheral SpA depending on the presence or absence of current back pain, independently of the other disease manifestations. Therefore, we aimed to assess the percentage of patients with axial SpA with peripheral disease and how this peripheral disease contributes to the overall disease activity.MethodsPrevalence and disease activity of peripheral disease manifestations were assessed in a real-life observational cohort of 314 patients with the clinical diagnosis of SpA and fulfilling the Assessment of SpondyloArthritis international Society (ASAS) criteria.ResultsOf the 314 patients fulfilling the ASAS criteria, 230 fulfilled the axial and 84 the peripheral SpA criteria. Of the 230 patients with axial SpA, 49% had purely axial disease without peripheral disease manifestations whereas 51% had combined axial (back pain) and peripheral (arthritis, enthesitis and/or dactylitis) disease. The latter group had the highest disease activity in comparison with pure axial SpA as well as with peripheral SpA.ConclusionHalf of the patients classified as axial SpA according to the ASAS criteria also have peripheral disease manifestations such as arthritis, enthesitis and/or dactylitis. These peripheral disease manifestations contribute significantly to overall disease activity.