Comparison of the ASAS Health Index in patients classified as radiographic axial spondyloarthritis (axSpA) or non-radiographic axSpA in the ASAS Health Index international validation study

Objectives To determine if there were differences in the Assessment of SpondyloArthritis international Society Health Index (ASAS HI) scores between patients classified as radiographic axial spondyloarthritis (r-axSpA) and non-radiographic axSpA (nr-axSpA), and to identify factors associated with higher ASAS HI scores in both disease phenotypes.Methods This study was an ancillary analysis of the ASAS HI international validation project performed in 23 countries. Patients were included if they were >= 18 years of age and diagnosed with axSpA. Univariable and multivariable analysis were performed to determine if ASAS HI scores differed between the axSpA phenotypes, and to identify other variables associated with ASAS HI scores. We also tested for potential interactions between the axSpA phenotype and significant variables identified through the multivariable regression.Results A total of 976 patients were included, with 703 having r-axSpA and 273 nr-axSpA. Patients with r-axSpA reported higher (worse) ASAS HI scores compared with those with nr-axSpA (6.8 (4.4) vs 6.0 (4.0), p=0.02), but the axSpA phenotype was not associated with ASAS HI scores in the multivariable regression (beta: -0.19, 95% CI: -0.56 to 0.19). Female gender, having worse physical function (Bath Ankylosing Spondylitis Functional Index), disease activity (Ankylosing Spondylitis Disease Activity Score) and anxiety and depressive symptoms (Hospital Anxiety and Depression Scale) were associated with higher ASAS HI scores. No interactions were found to be significant.Conclusion Overall health and functioning are similarly affected in patients with r-axSpA and nr-axSpA. Female patients, having worse physical function, disease activity, anxiety and depressive symptoms were independently associated with higher ASAS HI scores.