Clinical Characteristics of Potential "Difficult-to-treat" Patients with Psoriatic Arthritis: A Retrospective Analysis of a Longitudinal Cohort

Introduction The EULAR group recently published the definition of difficult-to-treat (D2T) patients for rheumatoid arthritis. However, a similar definition is lacking for patients with psoriatic arthritis (PsA), in which its multi-domain expression may impact the treatment response. The aim of the study was to characterize the potential D2T PsA patients, to assess the risk factors, and to determine the burden of disease. Methods Retrospective analysis of a longitudinal cohort of PsA patients attending a tertiary care center. At each visit, the patients underwent a complete physical examination and the clinical/laboratory data were collected. Data on comorbidities with the assessment of different comorbidity indices were also collected. Disease activity was assessed by using the DAPSA score and the MDA. The PsAID and HAQ-DI were also collected. We use the previous identified definition of D2T patients, applied to our PsA group and modified for this study. Results A total of 106 patients fulfilled the inclusion criteria and were evaluated. Of these, 36 (33.9%) patients fulfilled the criteria for the potential D2T patients. D2T patients showed a significantly higher BMI and higher prevalence of fibromyalgia. Furthermore, D2T patients showed a significantly higher median Functional Comorbidity Index and a significantly higher BSA, LEI, pain level, PsAID score, and HAQ-DI than non-D2T patients. Potential D2T patients also showed a significant delay in the time from diagnosis to first b/ts DMARDs treatment. Conclusions Our study firstly evaluated the presence of clinical characteristics of potential D2T patients and may contribute to future research on this intriguing aspect.