Prevalence of Fibromyalgia and Widespread Pain in Psoriatic Arthritis: Association With Disease Severity Assessment in a Large US Registry

Objective The classic conception of pain etiology in rheumatologic disease is nociceptive pain—tissue injury and inflammation signaling through peripheral and central nerve fibers. But this can be mixed with other pain etiologies, including nociplastic, which is augmented pain experience due to central sensitization. The pain of fibromyalgia (FM) is nociplastic, occurs in 10% to 30% of patients with rheumatologic disease, and its presence can influence disease severity assessment. The objective of our study was to (1) ascertain the prevalence of FM and widespread pain (WP) in the CorEvitas psoriatic arthritis (PsA) registry as assessed by the Widespread Pain Index (WPI) and Symptom Severity Scale (SSS) questionnaires; (2) characterize the demographic and clinical factors associated with FM and WP; and (3) ascertain the association of FM and WP on the Clinical Disease Activity in Psoriatic Arthritis (cDAPSA) score and other disease activity measures. Methods PsA registry patients completing the WPI/SSS questionnaires since May 2020, at their most recent visit recorded in the registry, were analyzed. Results The analysis included 1,823 patients with PsA; 11.1% fulfilled the FM definition and 20.6% fulfilled the WP definition. Several factors were associated with the FM definition, including female sex, depression and/or anxiety, impaired function, increased body mass index, and increased number of comorbidities. cDAPSA, patient pain and global assessment, and tender joint count were twice as severe in patients with FM compared to those without. Conclusion FM prevalence is elevated in PsA and is associated with elevated disease measures, confounding reliable disease assessment for treat‐to‐target goals. Identification of FM as an influential contextual factor in disease assessment is recommended.