Rheumatoid arthritis with concomitant fibromyalgia: The role of ultrasound in assessing disease activity

Introduction Fibromyalgia (FM) is a chronic painful condition frequently associated with rheumatoid arthritis (RA), which may falsely increase RA activity. The aim of our study was to compare clinical scoring and ultrasound (US) assessment in RA patients with concomitant FM with those without FM.Methods A cross-sectional study including patients with RA according to the ACR/EULAR 2010 criteria was conducted. Patients were divided into two groups: RA patients meeting ACR 2016 FM criteria (cases) and RA patients not meeting FM criteria (controls). Clinico-biological and US assessments of RA activity were performed on the same day for each patient.Results Eighty patients distributed into 40 patients in each group were recruited. Biologic DMARD prescription was more frequent in RA with FM patients than the control group (p = 0.04). DAS28 was significantly greater than DAS28 V3 in RA with FM group (p = 0.002). FM group had significantly less US synovitis (p = 0.035) and less Power Doppler (PD) activity (p = 0.035). Grey scale US score (p = 0.87) and DP US score (p = 0.162) were similar in the two groups. The correlation between the clinical and the ultrasonographic scores was strong to very strong in both groups with the strongest correlation found between DAS28 V3 and US DAS28 V3 (r = 0.95) in RA + FM group.Conclusion Our study confirms the overestimation of disease activity by the clinical scores in RA with concomitant FM. DAS28 V3 score and US assessment would represent a better alternative.