OBJECTIVES: To describe the baseline characteristics, bDMARD response and drug survival of axSpA patients in the British Society for Rheumatology Biologics Register in Ankylosing Spondylitis (BSRBR-AS) according to radiographic status.
METHODS: BSRBR-AS is a national prospective cohort including axSpA participants classified according to the ASAS criteria. In this analysis, baseline data of patients starting bDMARDs were compared. Ankylosing Spondylitis Disease Activity Scores (ASDAS) for low disease status, clinically important improvement (CII) and major improvement (MI) at one year were used to assess treatment response. Cox proportional hazard analysis was performed after adjusting for clinically relevant cofounders.
RESULTS: 1,145 axSpA patients were included. Higher male prevalence, older age and longer disease duration was seen in the r-axSpA subgroup. Based on a complete case analysis (290 patients), two thirds of patients achieved ASDAS low disease state at one year regardless of radiographic status (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 hazard ratio for nr-axSpA/axSpA was 0.94 (95% CI 0.69-1.28) when adjusted for sex, age, baseline ASDAS-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.
Bibliographical noteAcknowledgements: We acknowledge Prof. Gary J. MacFarlane as chief investigator on the BSRBR-AS study. We are grateful to the staff of the BSRBR-AS register and to the recruiting staff at the clinical centres, details of which are available at www.abdn.ac.uk/bsrbr-as. H.M.O. designed the study proposal. X.M. analysed the data and wrote the manuscript, with significant input from all co-authors. G.T.J. is deputy chief investigator on the BSRBR-AS study and together with L.D. discussed results and provided input into drafts of the manuscript. The study was approved by the National Research Ethics Service Committee North East-County Durham and Tees Valley (reference 11/NE/0374) and informed consent was obtained from all participants.
Funding: This work was supported by a research grant from the FOREUM Foundation for Research in Rheumatology. The BSRBR-AS is funded by the British Society for Rheumatology, which received funding for this from Pfizer, AbbVie and UCB. They have no input in determining the topics for analysis or work involved in undertaking it.
- ankylosing spondylitis
- biological therapy
- drug survival
- axial spondyloarthritis