Tender to touch-Prevalence and impact of concomitant fibromyalgia and enthesitis in spondyloarthritis: An ancillary analysis of the ASAS PerSpA study

Abstract

Objectives: The primary objective was to evaluate the co-existence of fibromyalgia (FM) & enthesitis in individuals with spondyloarthritis (SpA). Secondary objectives were to identify clinical features associated with the presence of FM in enthesitis and analyse sex-specific differences.

Methods: This was an ancillary analysis of the Assessment of SpondyloArthritis International Society Peripheral Involvement in SpA (PerSpA) study. Enthesitis was defined as the presence of enthesitis ever. Clinical FM was defined as the rheumatologist's confirmation of the presence of FM. A score of≥5/6 on the Fibromyalgia Rapid Screening Test (FiRST) defined a positive screening test for FM.

Results: Enthesitis ever and FM (EFM) co-existed in 10.3% (n=425) of the cohort using FiRST criteria and 5.3% using clinical diagnosis of FM. More individuals with FM by clinical diagnosis had imaging-confirmed enthesitis ever than by FiRST criteria. More females had EFM than males, defined clinically (76.9% vs 23.1%) or by FiRST criteria (62.6% vs 37.4%). Individuals with EFM had more severe disease across all measures compared to those with enthesitis only, with no significant difference between sexes. EFM was significantly associated with age, female sex, BMI, BASDAI and region.

Conclusion: FM is an important comorbidity in the setting of enthesitis in SpA. While EFM is more common in females, it is not a rare condition in males. EFM is associated with worse disease severity measures in SpA in both males and females. Recognition of FM in the setting of enthesitis is essential to prevent overtreatment and optimise patient outcomes.

Keywords: Axial spondyloarthritis; Comorbidities; Enthesitis; Fibromyalgia.