Inequity in biological DMARD prescription for spondyloarthritis across the globe: results from the ASAS-COMOSPA study

The value of biological disease-modifying antirheumatic drugs (bDMARDs) in spondyloarthritis (SpA) is well recognised, but global access to these treatments can be limited due to high costs and other factors. This study explores country variation in the use of bDMARDs in SpA in relation to country-level socioeconomic factors. Patients fulfilling the Assessment in SpondyloArthritis International Society (ASAS) SpA criteria in the multinational, cross-sectional ASAS Comorbidities in Spondyloarthritis study were studied. Current use of bDMARDs or conventional synthetic DMARDs (csDMARDs) was investigated in separate models, with multilevel logistic regression analysis, taking the country level into account. Contribution of socioeconomic factors, including country health expenditures, gross domestic product and human development index as independent country-level factors, was explored individually, in models adjusted for sociodemographic as well as clinical variables. In total, 3370 patients from 22 countries were included (mean (SD) age 43 (14) years; 66% male; 88% axial disease). Across countries, 1275 (38%) patients were bDMARD users. Crude mean bDMARD use varied between 5% (China) to 74% (Belgium). After adjustment for relevant sociodemographic and clinical variables, important variation in bDMARD use across countries remained (P <0.001). Country-level socioeconomic factors, specifically higher health expenditures, were related to higher bDMARD uptake, though not meeting statistical significance (OR 1.96; 95% CI 0.94 to 4.10). csDMARD uptake was significantly lower in countries with higher health expenditures (OR 0.32; 95% CI 0.15 to 0.65). Similar trends were seen with the other socioeconomic variables. There remains important residual variation across countries in bDMARD uptake of patients with SpA followed in specialised SpA centres. This is independent of well-known factors for bDMARD use such as clinical and country-level socioeconomic factors