Pain sensitization in fibromyalgia. Cross-sectional associations between quantitative sensory testing of pain sensitization and fibromyalgia disease burden.

Background: Whether fibromyalgia burden is related to measures of sensitization, assessed by quantitative sensory testing (QST), is not clear. We examine the associations between sensitization and fibromyalgia disease burden as measured by the polysymptomatic sistress scale (PDS) and the fibromyalgia impact questionnaire (FIQ) (range 0-100).

Materials And Methods: Participants were recruited from referrals to a rheumatology outpatient clinic and the fibromyalgia diagnosis was verified by a rheumatologist. They completed the PDS and FIQ and underwent QST of pressure pain threshold (PPT) at five sites, temporal summation (TS), and conditioned pain modulation (CPM) estimated as post-stimuli/pre-stimuli PPT. The associations between QST and disease burden were analysed in linear regression models adjusted for age, sex, and body mass index.

Results: A total of 78 individuals with clinically verified fibromyalgia (90% women, mean age 40.9 years (SD 7.3)) were recruited. Overall mean PPT was associated with the FIQ total score (β-2.1, 95% CI-4.3, -0.0) and the function component (β-2.1, (-4.3, -0.0)). When examining the associations between PPT at individual sites and fibromyalgia disease severity, PPTs at the distal interphalangeal joint and tibialis anterior muscle were associated with both FIQ total score and the FIQ fatigue component. All associations were weak and insignificant after Bonferroni corrections.

Conclusion: In this cohort of individuals with fibromyalgia, sensitization was not significantly associated with self-reported disease burden. Our results point to the multifactorial nature of fibromyalgia disease severity.

Significance: In patients with fibromyalgia, commonly used measures of sensitization do not explain the symptom burden or the functional impact.