How to measure disease activity in axial spondyloarthritis?
The evaluation of disease activity in axial spondyloarthritis (SpA) is complex and multifactorial. Moreover, patients and physicians have different perspectives of the disease and none of the current single-item or combined indexes adequately unifies both perspectives. Recent efforts have been made to improve disease activity measurement in axial SpA. The Assessment of Spondyloarthritis international Society (ASAS) embraced the project of developing a new index for disease activity measurement in axial SpA: the Ankylosing Spondylitis Disease Activity Score (ASDAS). The process closely mimicked the development of the Disease Activity Score in rheumatoid arthritis. Cut-offs for disease activity states and response levels have also been developed. Good performance of ASDAS has been shown in several international datasets, including randomized controlled trials and observational cohorts. The ASDAS is a well balanced index covering the underlying construct of disease activity and designed to avoid redundancy. It is a feasible and valid measurement instrument with a very good performance compared to existing tools. The ASDAS and its cut-off values may help clinicians and researchers to better assess patients with axial SpA, more reliably determine their disease activity status, the effectiveness of treatments and whether they are providing clinically meaningful improvement.