Fibromyalgia among patients presenting to a rheumatology clinic: prevalence and diagnosis

Introduction: Fibromyalgia (FM) syndrome is a chronic musculoskeletal disorder with extensive symptoms. Its most characteristic manifestation is the presence of persistent and diffuse chronic pain. The prevalence of this disease is 1% to 6% in different studies. Its exact nature and manifestations are not fully known; hence the empirical diagnosis of doctors and the proposed diagnostic criteria may differ in diagnosis. Objectives: This study aims to investigate the prevalence of FM symptoms among rheumatology patients, identify components of symptom and laboratory markers, and determine the interrater agreement between clinician judgment and diagnostic criteria. Patients and Methods: During one year, all patients referred to the rheumatology clinic were selected by simple sampling and underwent medical history collecting and physical examination by a single experienced rheumatologist, and the clinician’s judgment on the diagnosis of FM in the patients was recorded. Also, the American College of Rheumatology (ACR) standard questionnaire was used to evaluate the diagnosis of FM. Results: Between May 2018 and May 2019, 1762 patients were recruited, of whom 1428 (81%) were female, and 334 (19%) were male, with a mean age of 48.4±13.4 years. According to the rheumatologist and ACR criteria, 620 (35.1%) and 491 (27.8%) were diagnosed with FM respectively. Analysis indicated a lower agreement between the two in patients with underlying rheumatologic conditions of a mechanical origin. Younger age in patients with FM (P<0.001). A higher prevalence of FM was found among women (P<0.001). There was a significant correlation between concomitant rheumatologic conditions and FM occurrence (P=0.0004). Symptoms were clustered into 10 components with the component including fatigue explaining 22.18% of the variance in the results. Laboratory markers were clustered into 5 components. Conclusion: Fibromyalgia is a widespread disease among women that is frequently comorbid with other rheumatologic conditions. Agreement between ACR criteria and rheumatologist judgment is acceptable but can be improved by examining the symptoms in clusters rather than individually.