BASDAI and ASDAS disease states in relationship to ASAS40 response: post hoc analysis of ixekizumab in radiographic axial spondyloarthritis.

Objectives: To explore the relationship between Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Axial Spondyloarthritis Disease Activity Score (ASDAS) used in clinical practice and the Assessment of SpondyloArthritis international Society 40% (ASAS40) response, the primary endpoint in clinical trials in axial spondyloarthritis (axSpA).

Methods: Data from COAST-V, a phase 3 trial of ixekizumab vs placebo in biologic-naïve radiographic axSpA (r-axSpA) patients, were analysed. Patients treated with ixekizumab every 4 weeks were categorized using the ASAS40 response at week 16 and 52. The association between BASDAI and ASDAS disease states, respectively, and ASAS40 response achieved/not achieved was investigated. Additionally, back pain, fatigue, Bath Ankylosing Spondylitis Functional Index, ASAS Health Index and 36-item Short Form Health Survey Physical Component Summary scores corresponding to these states were assessed. Results were reported descriptively.

Results: After 16  weeks, 48.1% (39/81) of patients achieved an ASAS40 response. Among them, 71.8% (n = 28) and 43.6% (n = 17) achieved BASDAI <3 and BASDAI <2, respectively; 76.9% (n = 30) and 33.3% (n = 13) attained ASDAS <2.1 and ASDAS <1.3, respectively. Among ASAS40 responders at week 52 [53.1% (43/81)], 83.8% (n = 36) and 51.2% (n = 22) of patients achieved BASDAI <3 and BASDAI <2, respectively; 93.1% (n = 40) and 41.9% (n = 18) attained ASDAS <2.1 and ASDAS <1.3. Lower BASDAI and ASDAS disease states corresponded well with less back pain, fatigue and functioning impairment and better health-related quality of life.

Conclusions: More than 70% of biologic-naïve r-axSpA patients who achieved an ASAS40 response, also attained low disease activity or inactive disease as measured by the BASDAI or ASDAS. Findings may help clinicians translate results from clinical trials into daily practice.