Association between HLA-B27 and peripheral spondyloarthritis phenotype: results from the ASAS perSpA study.

Objective: To analyse the influence of HLA-B27 in the phenotypical expression of peripheral spondyloarthritis (pSpA).

Method: This is an observational cross-sectional study using data from the Assessment of SpondyloArthritis international Society perSpA registry, including all patients with an available HLA-B27 test result and with a diagnosis of pSpA or psoriatic arthritis (PsA) as per rheumatologist's judgement. Demographic and clinical data, presence of extra musculoskeletal manifestations (EMM) and fibromyalgia were the variables included in a simple and multiple logistic regression model to assess their association to HLA-B27 positivity.