Similar biologic drug response regardless of radiographic status in axial spondyloarthritis: data from the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis registry

Abstract

Objective: To describe the baseline characteristics, biologic DMARD (bDMARD) response and drug survival of axial SpA (axSpA) patients in the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis (BSRBR-AS) according to radiographic status.

Methods: The BSRBR-AS is a national prospective cohort including axSpA participants classified according to the Assessment of SpondyloArthritis international Society criteria. In this analysis, baseline data of patients starting bDMARDs were compared. Ankylosing Spondylitis Disease Activity Scores (ASDASs) for low disease status, clinically important improvement (CII) and major improvement (MI) at 1 year were used to assess treatment response. Cox proportional hazards analysis was performed after adjusting for clinically relevant confounders.

Results: A total of 1145 axSpA patients were included. Higher male prevalence, older age and longer disease duration were seen in the radiographic axSpA (r-axSpA) subgroup. Based on a complete case analysis (290 patients), two-thirds of patients achieved an ASDAS low disease state at 1 year regardless of radiographic status [non-radiographic axSpA (nr-axSpA) 64.2% vs r-axSpA 66.1]. No statistically significant differences were seen between the subgroups in attaining ASDAS CII (nr-axSpA 50.7% vs r-axSpA 44.7%) or MI (nr-axSpA 20% vs r-axSpA 18.7%). Drug survival probability curves were similar for both subgroups and the hazard ratio for nr-axSpA/axSpA was 0.94 (95% CI 0.69, 1.28) when adjusted for sex, age, baseline ASDAS with CRP, smoking status, disease duration, HLA-B27 and prescribed biologic.

Conclusions: Although there appeared to be some differences in the baseline characteristics when exploring this cohort according to radiographic status, which are likely related to the natural history of the disease, the level of biologic response and drug survival was comparable between nr-axSpA and r-axSpA.

Keywords: ankylosing spondylitis; axial spondyloarthritis; biological therapy; drug survival; epidemiology.