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

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OBJECTIVES: We investigated the effect of disease activity-guided dose optimization (DAGDO) of TNF inhibitor (TNFi) on disease activity and TNFi dose in 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: (i) full dose continuation period, (ii) TNFi DAGDO period, and (iii) period with stable TNFi dose after DAGDO. A mixed-model analysis was used to estimate mean Disease Activity Score 28-joint count CRP (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: Three hundred and twenty-four patients (153 PsA and 171 axSpA) were included, with a 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 of 0.06 (95% CI: -0.09, 0.21) in mean DAS28-CRP was found 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: DAGDO of TNFi reduces drug exposure and has no negative effects on disease activity in PsA and axSpA patients compared with full dose continuation.