Age at onset in axial spondyloarthritis around the world: data from the Assessment in SpondyloArthritis international Society Peripheral Involvement in Spondyloarthritis study.

OBJECTIVE: Age at onset is useful in identifying chronic back patients at an increased risk of axial SpA (axSpA). However, the majority of data on which the criterion of age at onset <45 years is based originates from Europe. Therefore it is unknown if this criterion applies in other parts of the world. We aimed to assess the age at onset of axSpA and its relationship with HLA-B27 and gender across the world. METHODS: Analyses were applied to patients from 24 countries across the world with an axSpA diagnosis and known age at onset of axial complaints. Cumulative probability plots were used to display the cumulative distribution of age at onset of axial symptoms. Linear regression models were built to assess the effect of HLA-B27 and gender on age at onset of axial symptoms. RESULTS: Of 2579 axSpA patients, 92% had an age at onset of axial symptoms <45 years, with only small variations across the geographical regions [Asia, n = 574 (94%); Europe and North America, n = 988 (92%); Latin America, n = 246 (89%); Middle East and North Africa, n = 771 (91%)]. Age at onset of axial symptoms was consistently lower in HLA-B27-positive patients {median 25 years [interquartile range (IQR) 19-32] vs 31 [IQR 22-39]} and male patients [median 25 years (IQR 19-33) vs 28 (IQR 21-37)], but in multivariable models an additional statistically significant effect of male gender independent of HLA-B27 was only found in Asia. CONCLUSION: Around the world, the great majority of axSpA patients had an age at onset of axial disease of <45 years, with HLA-B27 and male gender associated with earlier disease onset.

Associations between syndesmophytes and facet joint ankylosis in radiographic axial spondyloarthritis patients on low-dose CT over 2 years.

OBJECTIVES: In radiographic axial spondyloarthritis (r-axSpA), spinal damage manifests as syndesmophytes and facet joint ankylosis (FJA). We evaluated whether the presence of one lesion increased the risk of the other lesion. METHODS: Patients with r-axSpA underwent low-dose CT (ldCT) and MRI of the whole spine at baseline and 2 years. On ldCT, vertebrae were scored for presence and size of syndesmophytes; facet joints were assessed for ankylosis. MR images were assessed for inflammation. Two hypotheses were tested: (i) presence of FJA is associated with new syndesmophyte(s) on the same vertebral unit (VU) 2 years later, and (ii) presence of bridging syndesmophyte(s) is associated with new FJA on the same VU 2 years later. Two generalized estimating equations models were tested per hypothesis using increase of FJA/syndesmophytes (model A) or presence of FJA/syndesmophytes (model B) as outcome, adjusted for inflammation at baseline. Secondary analyses tested the hypotheses with outcomes on adjacent VUs and dose-response effects. RESULTS: Fifty-one patients were included (mean age 49, 84% male, 82% HLA-B27+). Baseline bridging syndesmophytes occurred more often (range: 10-60% per VU) than FJA (range: 8-36%). Odds ratios (ORs) (95% CI) for presence of bridging syndesmophytes on development of FJA were 3.55 (2.03, 6.21) for model A and 3.30 (2.14, 5.09) for model B. ORs for presence of baseline FJA on new syndesmophytes were 1.87 (1.20, 2.92) for model A and 1.69 (0.88, 3.22) for model B. Secondary analyses yielded positive ORs for both hypotheses. CONCLUSIONS: Bone formation in vertebrae and in facet joints influence each other's occurrence, with the effect of syndesmophytes being larger than that of FJA.

Does HLA-B*2706 protect against ankylosing spondylitis? A meta-analysis.

The human leukocyte antigen (HLA)-B*2706 is a relatively rare subtype of HLA-B27. In contrast to most HLA-B27 subtypes, some studies have reported HLA-B*2706 to be protective against ankylosing spondylitis (AS). A systematic review and a meta-analysis of available studies was performed to investigate the association of HLA-B*2706 with AS. After literature review a random effect meta-analysis was performed. No studies were found comparing the frequency of HLA-B*2706 in AS patients and controls. Meta-analysis of seven studies using HLA-B27-positive AS patients and controls showed a protective effect of HLA-B*2706 on development of AS in HLA-B27 individuals (odds ratio = 0.128, 95% CI = 0.043-0.378, P < 0.001). The results of the meta-analysis of HLA-B*2706 in HLA-B27-positive patients and controls is preliminary evidence of a protective effect of HLA-B*2706 against AS in the population. There is a clear need for additional studies on HLA-B*2706 in AS. Due to the fact that HLA-B*2706 is more or less restricted to Southeast Asia, researchers in this part of the world may have an essential role in performing these studies.