Characteristics of Difficult-to-Treat Psoriatic Arthritis: A Comparative Analysis

Objective: The EULAR task force recently published the difficult-to-treat rheumatoid arthritis (D2T RA) criteria, however, a definition of D2T patients in psoriatic arthritis (PsA) is still lacking. To date, we have little data concerning D2T PsA, especially in real-world. One of the limitations of the D2T RA EULAR definition is the absence of a temporal criterion. The primary endpoint of this work was to study the characteristics of D2T PsA patients using the EULAR definition. The second objective was to study a sub-group of patients with a predefined more stringent definition including a temporal criterion.Methods: A retrospective study was performed in a tertiary center. D2T PsA was defined as failure of ≥ 2 b/tsDMARDs with different mechanism of action. Very D2T PsA 2 was defined as failure of ≥ 2 b/tsDMARDs in less than 2 years of follow-up. D2T and Very D2T PsA patients were compared to nD2T PsA patients using pre-specified statistical tests.Results: 150 PsA patients were included: 49 D2T PsA and 101 nD2T PsA. D2T PsA was associated with a higher prevalence of axial involvement (p=0.030), axial and/or peripheral structural damage (p=0.006) at baseline and more bDMARDs discontinuation due to poor dermatological control (p=0.005). There was no significant difference regarding comorbidities such as obesity, smoking status, fibromyalgia or depression. In multivariate analysis, structural damage at baseline was found to be a predictive factor for D2T PsA with an OR of 2.49 (1.05 to 5.89; p=0.038).17 PsA (11.3%) patients were categorized as Very D2T PsA. When compared to nD2T group, proportion of obesity was higher (p=0.015) and axial involvement was more prevalent in the Very D2T group (p=0.020).Conclusion: D2T PsA patients had a higher prevalence of axial involvement, structural damage and therapeutic discontinuation due to poor dermatological control whereas Very D2T PsA patients were more likely obese with axial involvement. Very D2T PsA represent a minim proportion among patients when applying a more stringent definition. Pending the PsA D2T definition by the European and American societies, this study highlights some characteristics that may help practitioners better identify D2T patients.