Anti-polymer antibodies are correlated with pain and fatigue severity in patients with fibromyalgia syndrome

Objective: To investigate the prevalence of antipolymer antibody (APA) in patients with fibromyalgia (FM) and to examine its association with FM severity symptoms. Methods: The study population consisted of 79 FM patients and 75 controls: 32 with psoriatic arthritis and 43 with rheumatoid arthritis APA levels were indirectly assayed using a commercial ELISA kit from Corgenix (Westmister, Colorado, USA). Optical density (OD) values were recorded on duplicates of each of the reference and patient samples. Among clinical variables we investigated pain, measured according to visual analog scales (VAS: 0-100), fatigue, stiffness, anxiety, depression, all measured by VAS (0-100), and health status measured by Fibromyalgia Impact Questionnaire (FIQ). Results: Sixteen of the 79 FM patients (20.3%) and 12/78 controls (15.4%) were positive for APAs (P=0.536). Following ROC analysis, area under curve (AUC) was 0.49 (95% CI: 0.40, 0.58). Focusing on FM patients, we observed a correlation between APA titre and pain (τ: -0.221; P=0.020) and fatigue (τ: -0.205; P=0.032) at univariate analysis. Binomial regression analysis, controlling for clinical and demographic variables, showed that pain (PPR: 0.923; P=0.007) and fatigue (PPR: 0.948; P=0.024) were significantly associated with APA test sensitivity. Conclusions: APA test exhibited a low sensitivity in FM patients and it did not distinguish this group of patients from the controls enrolled in this study. Interestingly, positive APA test prevalence increased with less severe pain or fatigue.