Objective: To study the association of the presence of fibromyalgia (FM) with the Disease Activity Score in 28 joints (DAS28), the Health Assessment Questionnaire (HAQ), and the Medical Outcomes Study Short Form 36 (SF-36) health survey in patients with rheumatoid arthritis (RA).
Methods: A total of 270 outpatients with RA were enrolled in a prospective cross-sectional study. The patients underwent clinical evaluation and application of the HAQ and SF-36 questionnaires. Disease activity was evaluated using the DAS28 score. FM and RA diagnoses were made according to American College of Rheumatology criteria.
Results: The overall prevalence of FM was 13.4%. This group of patients had a higher prevalence of female sex, older mean age, higher functional class, and longer morning stiffness than patients with only RA. Mean +/- SD DAS28 scores were significantly higher in patients with RA and FM (5.36 +/- 0.99) than in patients with RA only (4.03 +/- 1.39; P < 0.001). In a multivariable linear regression analysis, FM was an important predictor of the DAS28 score, even after adjusting for the erythrocyte sedimentation rate, number of swollen joints, functional class, number of disease-modifying antirheumatic drugs currently in use, current dose of steroids, and articular erosions. HAQ and SF-36 scores were also worse in patients with RA and associated FM.
Conclusion: FM is related to worse scores on the DAS28, HAQ, and SF-36 in patients with RA. The presence of FM may have major implications in the interpretation of the DAS28 score because it is related to higher scores independently of objective evidence of RA activity.