Prevalence, outcomes, and predictive factors: a systematic literature review to inform the development of EULAR Points to Consider for the definition of Difficult-to-Manage and Treatment-Refractory psoriatic arthritis

Objectives: To perform a systematic literature review (SLR) to inform the EULAR Task Force "Points to Consider for the definitions of Difficult-to-Manage (D2M) and Treatment-Refractory (TR) psoriatic arthritis (PsA)". Methods: The SLR addressed 3 separate questions concerning the following: (1) prevalence, (2) outcomes, and (3) predictors of D2M/TR PsA. A search was conducted in MEDLINE (Ovid), Cochrane Database of Systematic Reviews, CENTRAL, EMBASE, and Epistemonikos from inception to March 3, 2024, as well as EULAR/ACR abstracts for 2023/24 and 2022/23, respectively. This systematic review adhered to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and was registered on PROSPERO. Data are summarised descriptively. Meta-analysis was not possible due to significant heterogeneity and/or lack of high-quality evidence. Risk of bias (RoB) was assessed using the Newcastle-Ottawa Scale. Results: Overall, 70, 4, and 25 articles/abstracts were included for questions 1, 2, and 3, respectively. For question 1, 30/70 records had low/moderate RoB, with the prevalence of D2T PsA ranging from 5% to 80% depending on both the timepoint at which prevalence was measured and the definition of D2M/TR PsA applied, which varied significantly between studies. For question 2, all records had a high RoB; therefore, no conclusions could be drawn. For question 3, all records had a moderate RoB, and 84 categories of potential predictors were identified, with large differences in strength and direction of association between studies. Conclusions: Despite significant heterogeneity in the published literature regarding the scope, definition, long-term outcomes, and predictors of D2M/TR PsA, certain patterns emerged that helped shape the final EULAR Task Force recommendations.