RT Journal Article SR Electronic T1 Evaluation of long-term TNFi effectiveness after a first switch in early axial spondyloarthritis considering time-varying prescription bias: an inverse-probability weighting analysis of the DESIR cohort JF RMD Open JO RMD Open FD EULAR SP e001846 DO 10.1136/rmdopen-2021-001846 VO 8 IS 1 A1 Pons, Marion A1 Chevret, Sylvie A1 Briot, Karine A1 d’Agostino, Maria-Antonietta A1 Roux, Christian A1 Dougados, Maxime A1 Molto, Anna YR 2022 UL http://rmdopen.bmj.com/content/8/1/e001846.abstract AB Objective To evaluate long-term effectiveness of tumour necrosis factor inhibitor (TNFi) after a first switch, and their associated factors in an early axial spondyloarthritis (axSpA) population, considering time-varying prescription bias.Methods Observational prospective cohort (DEvenir des Spondylarthropathies Indifférenciées Récentes) with 5 years of follow-up, including 708 TNFi-naïve patients with early axSpA. Long-term effectiveness of TNFi after a first switch (ASAS40 response after at least 2 visits under treatment) were estimated using marginal structural models (implementing inverse-probability weighting and iterative propensity scores). Factors associated with the outcome were explored by multivariate Cox regression models.Results The hazard to present an ASAS40 response after a first TNFi switch was increased (HR=2.4 (95% CI 1.9 to 3.0)); this response ratio was slightly lower compared with the response in TNFi naïve patients after a first TNFi (HR=3.3 (95% CI 2.9 to 3.8)). HLA-B27 positive was the only factor independently associated with ASAS40 response after a first TNFi switch.Conclusion After application of innovative methods to overcome time-varying prescription bias, the magnitude of the TNFi response after a first switch was found to be numerically lower but clinically relevant from the response in TNFi-naïve patients.Data may be obtained from a third party and are not publicly available. not applicable.