As with fibromyalgia, several musculoskeletal disorders are characterized by chronic pain, raising a clinical question – do the instruments used to assess fibromyalgia symptoms according to ACR criteria (ACR criteria) generate similar scores in other chronic musculoskeletal pain?

To compare the pain, functionality, and symptoms between fibromyalgia and other chronic musculoskeletal pain using the Widespread Pain Index (WPI) and the Symptom Severity Scale (SSS).

This is a cross-sectional study. Participants over 18 years old were included if they presented the report of chronic musculoskeletal pain (≥ 3 months), and after that, they were divided into two groups (fibromyalgia and chronic pain). They answered the Fibromyalgia Impact Questionnaire-Revised (FIQ-R), Brief Pain Inventory (BPI), Numerical Pain Rating Scale (NPRS) for pain and fatigue, WPI, and SSS.

A total of 166 participants were included in this study into two independent groups (chronic pain, n=83; fibromyalgia, n=83). We observed significant differences (p < 0.05) and large effect sizes (Cohen's d, ≥ 0.7) in clinical outcomes comparisons between groups (i.e., widespread pain, symptom severity, present pain at rest, and after movement, fatigue; pain severity, and impact; function, global impact, and fibromyalgia symptoms).

Fibromyalgia patients (2016 ACR criteria) compared to other chronic musculoskeletal pain patients have higher levels of pain (at rest or after movement) and fatigue, greater impairment in both functionality and global impact, and worse symptoms.

WPI and SSS instruments should be used exclusively to assess fibromyalgia symptoms.