Residual Disease Activity and Burden of Disease in Canadian Patients With Axial Spondyloarthritis: Results From a Multiregistry Analysis (UNISON-Axial SpA).

Objective: There is a key knowledge gap in quantifying residual disease activity in Canadian patients with axial spondyloarthritis (axSpA). The objective of this study was to evaluate and describe residual disease activity and burden of disease in Canadian patients with axSpA.

Methods: This was an observational, retrospective analysis of data extracted from the Rhumadata (Québec), Spondyloarthritis Research Consortium of Canada (SPARCC; East/Atlantic and West regions, as well as Ontario), and Follow-up Research Cohort of Ankylosing Spondylitis (FORCAST; Alberta) registries. The primary endpoint was the proportion of patients who failed to achieve sustained low disease activity (LDA) at 12 months. LDA was defined as a Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score < 3 and sustained LDA was defined as achieving LDA at both 6 and 12 months after the most recent change in treatment. Analyses included outcomes by treatment class (nonsteroidal antiinflammatory drugs, tumor necrosis factor inhibitor, or interleukin 17 inhibitor).

Results: A total of 980 patients (Rhumadata, N = 488; SPARCC, N = 239; FORCAST, N = 253) were included. Nearly half of patients with axSpA from Rhumadata (49.5%) and FORCAST (55.3%) and 65.8% of those from SPARCC failed to achieve LDA (BASDAI < 3) at 6 months after treatment initiation. At 12 months, failure to achieve sustained LDA rose to 62% in Rhumadata, 65.1% in FORCAST, and 81% in SPARCC. Pain persisted in nearly half of all patients.

Conclusion: This analysis demonstrated that most Canadians with axSpA failed to achieve sustained LDA after 12 months of initiating their latest therapy and confirms a high unmet need for additional treatments.