Background The polysymptomatic distress scale (PSD) is considered a measure of FM severity and ranges from 0 to 31. It is calculated by adding the two components of the American College of Rheumatology (ACR) 2010 fibromyalgia (FM) criteria, widespread pain index (WPI) and symptoms severity scale (SS).

Objectives Determine the relationship between depression, anxiety, function disability and pain related disability, with fibromyalgia severity as measured by PSD and its subsets, WPI and SS.

Methods All consecutive FM patients who met the ACR 2010 criteria completed the following questionnaires: PSD, patient health related questionnaire (PHQ-9), a measure of depressive symptoms, general anxiety disorder questionnaire (GAD-7), health assessment questionnaire disability index (HAQ-DI), and pain disability index (PDI).

Results Of 169 patients, 85.7% were women, mean age 42.3 (13.3), BMI 29.3 (7.1), PHQ-9 13.7 (5.2), GAD-7 10.2 (9.1), HAQ-DI 1.6 (2.9), PDI 6 (2.1), WPI 14.3 (2.7), SS 10 (1.6). In univariate analysis PSD correlated significantly (p<0.01) with PHQ-9 (0.576), PDI (0.422), and GAD-7 (0.356). Widespread pain index correlated significantly with PHQ-9 (0.313), GAD-7 (0.239), HAQ-DI (0.259), and PDI (0.296). Symptom severity scale correlated significantly with PHQ-9 (0.496), GAD-7 (0.337), HAQ-DI (0.275), PDI (0.340). A linear regression analysis model, which included PHQ-9, GAD-7, PDI and HAQ-DI predicted 0.269 of PSD variance, p=0.001, and only PDI remained significantly correlated with PSD. A similar model predicted 0.348 of SS variance, (P<0.0001), and only PHQ-9 remained significantly correlated with SS. This model did not significantly predict WPI variability.

Conclusions Depression, anxiety, pain disability and functional disability predict a small variance of fibromyalgia severity measured by PSD. In regression analysis, pain disability measured by PDI is the only variable that remains independently correlated with PSD. None of these variables predicted WPI, while depression measured by PHQ-9 remains independently correlated with SS, indicating that PSD subsets measure different dimensions of FM.

Disclosure of Interest None declared