Construct validity of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and Ankylosing Spondylitis Disease Activity Score (ASDAS) treatment target cut-offs in a BASDAI treat-to-target axial spondyloarthritis cohort: a cross-sectional study.

Our study showed moderate and comparable construct validity for BASDAI- and ASDAS-based disease activity states, with the expected exception of association with CRP. Therefore, no strong preference can be given for either measure, although the ASDAS seems marginally more valid.