Vitamin D status in spondyloarthritis: results of the ASAS-COMOSPA international study.

Objectives: Spondyloarthritis (SpA) encompasses both bone production and bone loss, and the latter is particularly linked to inflammation. Vitamin D deficiency has been associated with several inflammatory conditions (i.e. cardiovascular disease, rheumatoid arthritis), but it has been poorly evaluated in SpA patients. We aimed to a) describe the prevalence of vitamin D deficiency in SpA patients worldwide; b) compare SpA patients with and without vitamin D deficiency in terms of disease phenotype, activity severity and comorbidities.

Methods: This is an ancillary study of the ASAS-COMOSPA study initiative, an international cross-sectional study of patients with SpA. Demographics, patients' phenotype, disease activity/severity measures and comorbidities were assessed. Serum 25-hydroxyvitamin D (25OHD) deficiency was defined as <20 ng/mL (<50 nmol/L).

Statistical Analysis: a) prevalence of vitamin D deficiency; b) comparison of the disease presentation/activity/severity and comorbidities in the group of patients with and without vitamin D deficiency by bi-variable and multivariable analysis.

Results: Vitamin D deficiency was observed in 527(51.2%) of the 1030 patients with available data who were not receiving any supplementation. Vitamin D deficiency was independently associated with the presence of radiographic sacroiliitis (OR=2.1 [95%CI1.3; 3.3]) and a 25OHD measured in winter and spring (OR=1.88 [95%CI 1.2; 2.9]). No independent association between vitamin D deficiency and comorbidities was found.

Conclusions: This study suggests that vitamin D deficiency is common in SpA worldwide and is associated with season but also with more severe forms of SpA.