Thresholds for efficacy outcomes in psoriatic arthritis vary according to baseline disease activity but not according to prior tumour necrosis factor inhibitor treatment.

Abstract

OBJECTIVES: Efficacy thresholds allow interpretation of randomised clinical trials (RCTs) and establishment of treatment targets. To assess the need for more personalised treatment goals, minimal clinically important improvement (MCII) thresholds in psoriatic arthritis (PsA) clinical and patient-reported outcome measures were determined by treatment history and baseline disease activity.

METHODS: This post hoc analysis pooled data from 3 RCTs in participants with active PsA receiving guselkumab every 8 week (Q8W), or placebo with W24 transition to guselkumab Q8W. MCII thresholds for clinical Disease Activity Index for PsA (cDAPSA), PsA Disease Activity Score (PASDAS), and patient-reported assessments of arthritis and psoriasis, pain, fatigue, and physical function were determined using established distribution-based methods in participant subgroups defined by prior tumour necrosis factor inhibitor (TNFi) treatment and baseline cDAPSA and PASDAS disease activity (high vs moderate).

RESULTS: In this pooled RCT population, estimated MCII thresholds for all examined measures were consistent across TNFi-experienced and biologic-naive cohorts. However, the determined cDAPSA, but not PASDAS, MCII was more stringent among participants with high vs moderate baseline disease activity. Guselkumab-treated participants had greater odds of achieving MCII thresholds vs placebo as early as W8, irrespective of prior TNFi and baseline cDAPSA and PASDAS disease activity, supporting the known-groups validity of the estimated thresholds.

CONCLUSIONS: Estimated MCII thresholds were consistent regardless of prior TNFi but greater for participants with higher baseline joint disease activity, indicating disease severity may impact perceived PsA improvement. These findings may aid in setting more personalised goals in shared decision-making and treat-to-target strategies, and RCT interpretation.