Tumour necrosis factor inhibitor dose adaptation in psoriatic arthritis and axial spondyloarthritis (TAPAS): a retrospective cohort study.

Objectives We investigated the effect of disease activity-guided dose optimisation (DAGDO) of Tumour Necrosis Factor inhibitor (TNFi) on disease activity and TNFi dose in psoriatic arthritis (PsA) and axial Spondyloarthritis (axSpA) patients with low disease activity (LDA). Methods A retrospective cohort study was conducted in PsA and axSpA patients doing well on TNFi and eligible for TNFi DAGDO. Three different treatment periods were defined: 1) full dose continuation period; 2) TNFi DAGDO period; 3) period with stable TNFi dose after DAGDO. A mixed-model analysis was used to estimate mean Disease Activity Score 28-joint count C-reactive protein (DAS28-CRP) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) during these periods, and a mean percentage of the Daily Defined Dose (%DDD) was calculated as secondary outcome. Results 324 patients (153 PsA and 171 axSpA) were included, mean of 6.5 DAS28-CRP and 6.4 BASDAI measurements and a median follow-up duration of 46 and 44 months respectively. A corrected difference in mean DAS28-CRP was found of 0.06 (95% Confidence Interval (CI) [-0.09-0.21]) for the TNFi DAGDO period and 0.03 (95%CI [-0.14-0.20]) for the period with stable TNFi dose, compared with full dose continuation period. Differences for BASDAI were 0.03 (95%CI [-0.21-0.27]) and 0.05 (95%CI [-0.24-0.34]) respectively. The mean %DDD for the three treatment periods was for PsA 108%, 62% and 78%, and for axSpA 108%, 62%, and 72% respectively. Conclusion T2T tapering of TNFi reduces drug exposure and has no negative effects on disease activity in PsA and axSpA patients compared with full dose continuation.