Impact of concomitant fibromyalgia on disease activity assessment and quality of life in Vietnamese patients with rheumatoid arthritis.

Objectives: FM is increasingly recognised as a contributor to RA and may influence disease activity assessment. However, data from low- and middle-income countries remain limited. We aimed to investigate the prevalence and clinical impact of concomitant FM on disease activity assessment, quality of life (QoL) and treatment patterns in Vietnamese patients with RA. Methods: In this prospective cross-sectional study, adult patients with RA were assessed for FM using the 2016 ACR criteria. Disease activity [28-joint DAS with CRP (DAS28-CRP)], objective inflammatory markers, patient-reported outcomes, QoL and treatments were analysed. Multivariable linear regression analysis was performed to assess whether FM was independently associated with DAS28-CRP after adjustment for demographic and relevant clinical covariates. Results: Among 187 patients with RA, 34.2% fulfilled criteria for concomitant FM. Patients with FM had significantly higher DAS28-CRP scores compared with those without FM. The FM-related increase in DAS28-CRP was driven predominantly by subjective components, while objective inflammatory measures differed modestly. In multivariable analysis, FM remained independently associated with higher DAS28-CRP scores. Patients with FM also reported significantly worse QoL and were more likely to receive corticosteroids despite less frequent use of DMARDs. Conclusion: Concomitant FM is common among Vietnamese patients with RA and is associated with symptom amplification, poorer QoL and higher DASs independent of objective inflammation. In resource-limited settings, reliance on DAS28-CRP alone may contribute to symptom-driven treatment escalation and corticosteroid overuse. Recognition of FM is essential to support accurate disease assessment and safer, more appropriate management strategies.