Background Little is known about tumor-necrosis-factor-alpha-inhibitor (TNFi) treatment outcomes in Ankylosing Spondylitis (AS) vs. non-radiographic axial spondyloartrhitis (nr-axSpA).
Objectives To compare baseline disease activity and treatment outcomes in biologic naïve patients with AS and nr-axSpA, who initiate TNFi treatment in clinical practice taking potential confounders into consideration.
Methods We performed an observational cohort study based on prospectively registered data in the nationwide Danish quality registry, DANBIO, including baseline and 3–6 months' follow-up markers of disease activity (visual analogue score (VAS) global disease, Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), BAS metrology index (BASMI) and serum C-reactive protein (CRP)). Treatment response was defined as either a 50% or a 20 mm reduction in BASDAI after 3–6 mths treatment. We used Kaplan-Meier plots, Cox and logistic regression analyses to study the impact of diagnosis (AS vs. nr-axSpA) and potential confounders (gender, age, start year, HLA-B27, disease duration, TNFi type, smoking, baseline disease activity) on TNFi adherence and response. Numbers are medians (IQR) unless otherwise stated.
Results We identified 1,250 TNFi naïve patients in DANBIO with axSpA according to the treating physician. Of these, 50% had AS, 28% nr-axSpA and 21% lacked X-rays of sacroiliac joints. Baseline demographics and disease activity differed in nr-axSpA vs. AS (Table). Response rates were similar, but treatment adherence was poorer in nr-axSpA than in AS (univariate, Table). In confounder adjusted analyses, axSpA sub-diagnosis was not associated with response rates or treatment adherence. However, HLA-B27 positivity was associated with better treatment adherence (HLA-B27 neg/pos, nr-axSpA: HR 1.74 (1.29–2.36), AS: HR 2.04 (1.53–2.71.), both p<0.0001) (Figure) and higher response rates (nr-axSpA: 30%/55%, AS: 29%/54%, univariate, both p<0.05). Similar results for HLA-B27 were found in confounder-adjusted analyses.
Conclusions In this nationwide cohort, patients with nr-axSpA had higher subjective disease activity at the start of the first TNFi treatment but had similar confounder adjusted treatment adherences and response as AS pts. HLA-B27 positive pts had better outcomes irrespective of axSpA sub-diagnosis.
Disclosure of Interest B. Glintborg: None declared, I. Juul Sørensen: None declared, M. Østergaard: None declared, A. A. Mahamoud: None declared, N. S. Krogh: None declared, L. Andersen: None declared, J. Raun: None declared, O. Hendricks: None declared, M. Kowalski: None declared, L. Danielsen: None declared, S. Christensen: None declared, N. al Chaer: None declared, R. Pelck: None declared, H. Nordin: None declared, J. Pedersen: None declared, D. Kraus: None declared, I. Jensen Hansen: None declared, J. Espesen: None declared, A. Schlemmer: None declared, A. Loft Speakers bureau: MSD, L. Salomonsen: None declared, L. Dreyer: None declared, M. Hetland: None declared