Determinants of health-related quality of life in spondyloarthritis and rheumatoid arthritis - data from the COMOSPA and COMORA studies.

Objectives: To assess the hierarchy of outcomes contributing to health-related quality of life (HRQoL) in spondyloarthritis (SpA) and rheumatoid arthritis (RA).

Methods: Data from the international cross-sectional COMOSPA and COMORA studies were used. HRQoL was assessed using the EuroQOL 5-dimension 3-level (EQ-5D-3 L). First, multivariable linear regression models were used to identify associations between EQ-5D-3 L (dependent variable) and several demographic and clinical variables (independent variables). Second, a decision tree was built using Chi-square Automatic Interaction Detector, a method of unbiased hierarchical multivariable analysis (dependent variable: EQ-5D-3 L).

Results: In total, 3984 patients with SpA and 3920 patients with RA were included. In SpA, HRQoL was associated with BASFI (adjusted B=-0.006; 95%CI=-0.007 to -0.005), ASDAS (-0.052; -0.071 to -0.033), work productivity loss score (-0.002; -0.003 to -0.002), NSAID treatment (-0.052; -0.083 to -0.020), bDMARD treatment (-0.051; -0.082 to -0.021), university education (-0.051; -0.075 to -0.027) and radiographic sacroiliitis (0.035; 0.004 to 0.030). In RA, HRQoL was associated with modified Health Assessment Questionnaire (MHAQ) (-0.220, -0.253 to -0.188), DAS28-CRP-3v (-0.027, -0.036 to -0.018), work productivity loss score (-0.003, -0.003 to -0.002), presence of erosions (-0.042, -0.065 to -0.020), alcohol consumption ≥3 units/day (0.012, 0.001 to 0.024)) and csDMARD treatment (0.034, 0.001 to 0.066). The decision tree revealed BASFI and MHAQ as first variables with the most discriminative power on EQ-5D-3 L, followed by work productivity loss and disease activity, in both SpA and RA cohorts.

Conclusion: In SpA and RA, physical function is the main contributor to HRQoL measured by EQ-5D-3 L, followed by disease activity and work productivity loss.