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

Abstract

The Ankylosing Spondylitis (AS) Disease Activity Score (ASDAS) is largely used for assessing disease activity in patients with AS. We aimed to investigate the predictability of ASDAS on drug survival in patients with low Bath AS Disease Activity Index (BASDAI) during biologic therapy. Using data from multi-center, prospective, observational prospective cohort, Korean College of Rheumatology Biologics and Targeted Therapy (KOBIO) registry. 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 < 2.1, BASDAI < 4). Data from 1773 patients were analyzed. Among 269 patients with low BASDAI at baseline, 151 (56.1%) patients had high ASDAS-CRP, yet in 142 patients with low ASDAS-CRP at baseline, only 24 (16.9%) patients had a high BASDAI. High ASDAS-CRP captured more patients who had initiated or switched to a TNFi than those with high BASDAI (92.5% versus 84.8%, respectively, p < 0.001). Moreover, among AS patients with low BASDAI after 1 year of therapy, drug persistence in the following year was significantly lower in patients with high ASDAS than in those with low ASDAS (68.7% versus 82.5%, p < 0.001). ASDAS-CRP not only has its advantages over BASDAI in assessing disease activity but also low ASDAS-CRP at 1 year can be a marker of long-term drug survival of TNFi therapy.