Similarities and differences between patients fulfilling axial and peripheral ASAS criteria for spondyloarthritis: Results from the Esperanza Cohort.

OBJECTIVES: To describe and compare the characteristics of patients fulfilling the ASAS criteria for axial Spondyloarthritis (SpA) versus peripheral SpA .

METHODS: Baseline dataset from the ESPeranza cohort was used. In this programme, patients were referred to rheumatologist in case of (1) age <45 years, (2) symptoms duration 3-24 months and (3) inflammatory back pain (IBP) or asymmetrical arthritis or spinal/joint pain plus ≥1 SpA features. The programme was developed between April 2008 and June 2011. Data from 377 patients fulfilling the ASAS classification criteria for SpA were used. Descriptive analysis was employed to compare demographic and disease characteristics between patients with axial SpA versus peripheral SpA.

RESULTS: Two hundred and ninety (77.2%) patients were classified as axial SpA (109 ankylosing spondylitis and 182 non-radiographic SpA) while 86 (22.8%) patients had peripheral SpA. Age, gender distribution and degree of disease activity were similar in both groups. Patients with axial SpA were referred after having symptoms for a longer period and had more frequently uveitis and positive HLA-B27. Patients with peripheral SpA had in a greater percentage more working disability and had more frequently enthesitis, psoriasis, dactylitis and inflammatory bowel disease (IBD).

CONCLUSIONS: The ASAS classification criteria for SpA seem to classify patients within the same spectrum of disease beyond the predominant symptoms at onset. However, despite having similar degree of disease activity, time to be referred to rheumatologist is increased in axial SpA patients compared with peripheral SpA patients.