Difficult-to-treat axial spondyloarthritis is associated with psoriasis, peripheral involvement and comorbidities: results of an observational nationwide study.

OBJECTIVES:To determine the cumulative incidence and identify the factors associated with difficult-to-treat axial spondyloarthritis (D2T-axSpA) in French patients newly benefiting from the French 'long-term illness' (LTI) social security scheme for axial spondyloarthritis (axSpA). METHODS:This national cohort study was based on the French National Medico-Administrative Database, SNDS, which contains data on hospitalisation, LTI and outpatient care consumption. All French patients newly receiving LTI benefits for ankylosing spondylitis (AS) between 2010 and 2013 were included in the study. In France, LTI is required to access biological/targeted synthetic DMARDs (b/tsDMARDs). The follow-up period ended on 31 December 2018. So-called D2T-axSpA was defined as the failure of three b/tsDMARDs or of two b/tsDMARDs with different modes of action. Comorbidities and extra-musculoskeletal manifestations were identified using previously described algorithms. Characteristics were compared between patients with D2T-axSpA and patients with non-D2T-axSpA who had received at least one b/tsDMARD with bivariate and multivariate analysis using logistic regression. Incidence rates of major cardiovascular event (MACE) and death were compared using competitive risk analysis. RESULTS:22 932 patients were included. 10 798 (47.08%) patients received at least one bDMARD. None received tsDMARD. During follow-up, 2115 patients were classified as having D2T-axSpA, representing 19.59% of patients who received at least one bDMARD. In multivariate analysis, D2T-axSpA was significantly associated with female gender, peripheral involvement, psoriasis, hypertension and depression (p<0.001 for each case). There was no difference in the incidence of MACE (p=0.92) or death (p=0.87). CONCLUSION:D2T-axSpA affects one in five patients exposed to bDMARDs in this national cohort. D2T-axSpA is more common in women and patients with peripheral involvement and/or comorbidities.