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