ASAS recommendations on reporting axial spondyloarthritis clinical trials.

Objectives: This study aims to develop recommendations on reporting baseline features and outcomes from axial spondyloarthritis (axSpA) clinical trials based on the recently updated instrument set of the Assessment of SpondyloArthritis international Society (ASAS) core outcome set (COS).

Methods: A steering group (SG) convened a workgroup (WG), consisting of 13 ASAS members including rheumatologists, methodologists, epidemiologists, and 2 Young ASAS members. Recommendations on reporting axSpA trials baseline features and outcomes were developed in 3 steps: (1) the SG identified relevant baseline features from key axSpA clinical trials and formulated a proposal on how outcomes related to the instruments in the ASAS COS should be presented. (2) The SG proposal was presented, discussed, and modified in WG meetings. (3) WG proposal was discussed and voted on by ASAS members during the 2024 annual ASAS workshop.

Results: Forty-two baseline features relevant for all axSpA clinical trials and 8 additional features for disease-modifying drug trials were defined including descriptions on how to report them. Additionally, recommendations on how to report 20 trial outcomes at baseline and follow-up timepoints were put forward. Finally, recommendations on how to report 11 outcomes of instruments additionally endorsed by ASAS but not in the COS were formulated. Proposals for baseline features, COS outcomes, and outcomes not in COS were approved by ASAS members (with 84%, 85%, and 93% of members in favour, respectively).

Conclusions: These ASAS-endorsed recommendations on axSpA clinical trial reporting provide a standardised approach to reporting both baseline features as well as outcomes from axSpA clinical trials.