Effectiveness of TNF inhibitors in patients with very early axial spondyloarthritis, defined as duration of ≤1 year of back pain: longitudinal observational data from the SCQM registry.

Objective To characterise patients with 'very early' axial spondyloarthritis (axSpA), defined as a duration ≤1 year of back pain and to determine the effectiveness of a first tumour necrosis factor inhibitor (TNFi) in very early versus established axSpA in a large observational registry. Methods We included a total of 3324 patients with axSpA from the Swiss Clinical Quality Management in Rheumatic Diseases registry with available data on duration of back pain (≤1 year=very early axSpA, n=441; >1 year and ≤2 years=early axSpA, n=218; >2 years=established axSpA, n=2575). A first TNFi was started in 31%, 38% and 36% of patients with very early, early and established axSpA. Adjusted logistic regression models were used to compare the probability of achieving low disease activity status according to the Axial Spondyloarthritis Disease Activity Score (ASDAS <2.1) at 1 year. Drug survival was analysed with multiple-adjusted Cox proportional hazards models. Missing data were handled using multiple imputation by chained equations. Results Objective signs of inflammation were more prevalent in very early disease. No difference was found regarding the achievement of ASDAS <2.1 after adjustment for age, sex, human leucocyte antigen-B27 status, education, body mass index, smoking, ASDAS and sacroiliac inflammation on MRI (OR 1.08, 95% CI 0.70 to 1.68 in very early vs established axSpA). Similarly, no significant difference in TNFi retention was found in very early versus established axSpA (HR for drug discontinuation 1.05, 95% CI 0.84 to 1.31). Conclusion We found no evidence for a better effectiveness of TNFi in patients with very early versus established axSpA.