Assessment of Widespread and Extraarticular Pain in Psoriatic Arthritis: A Case-control Study.

Objective: A remarkable lack of detailed knowledge on pain areas in psoriatic arthritis (PsA) is present, and their clinical relevance is quite unknown. The main aim of the study was to explore pain areas in PsA, comparing them with those involved in patients with fibromyalgia (FM). In addition, a secondary aim was to investigate any possible association between pain areas and outcome measures in PsA.

Methods: This was a case-control study on patients with PsA satisfying Classification Criteria for Psoriatic Arthritis criteria and patients with FM. In all patients with PsA and FM, a body chart filled in by the patient reporting pain areas in 80 body locations was performed. The Widespread Pain Index (WPI) was performed in all patients with PsA and FM. In all patients with PsA, an assessment of disease activity, treatment target, function, and impact of disease was carried out.

Results: Fifty patients with PsA and 50 FM controls were evaluated. A significantly higher number of pain areas in the body chart and higher WPI scores were found in patients with FM when compared to patients with PsA. In PsA, the number of areas reported in the body chart significantly correlated with the Disease Activity Index for PsA, Health Assessment Questionnaire-Disability Index, and PsA Impact of Disease. Patients who showed a significantly high number of extraarticular pain areas involved were those who were not in remission/minimal disease activity, or who did not have a greater impact of disease or reduced function.

Conclusion: The main results showed that widespread and extraarticular pain was present in patients with PsA, showing that this nonarticular pain had an impact on important disease domains. The present study could contribute to an important aspect of this challenging and multifaceted disease-namely, the assessment of widespread pain.