The predictability of ASDAS on drug survival in patients with ankylosing spondylitis on biologic therapy: data from the KOBIO registry

Background: The Ankylosing Spondylitis (AS) Disease Activity Score (ASDAS) is largely used for assessing disease activity in patients with AS. Objectives: We aimed to investigate the predictability of ASDAS on drug survival in patients with low Bath AS Disease Activity Index (BASDAI) during biologic therapy. Design: Using data from multi-center, prospective, observational prospective cohort, Korean College of Rheumatology Biologics and Targeted Therapy (KOBIO) registry. Methods: The study population consisted of patients enrolled in the KOBIO registry from December 2012 to December 2018. The baseline demographic data and variables such as extra-articular manifestations, HLA-B27 positivity, family history of spondyloarthritis, ASDAS C-reactive protein (CRP), BASDAI, and Bath AS Functional Index scores were collected from the database. The disease activity indices were followed yearly after initiating a tumor necrosis factor (TNF) inhibitor (TNFi). Disease activities were defined as high (ASDAS-CRP ⩾ 2.1, BASDAI ⩾ 4) and low (ASDAS-CRP