What are the diagnosis criteria for fibromyalgia?

Fibromyalgia Diagnosis Criteria

Fibromyalgia is diagnosed using the American College of Rheumatology (ACR) criteria, which require chronic widespread pain lasting at least 3 months in all four body quadrants, accompanied by fatigue, sleep disturbances, and cognitive dysfunction, without requiring tender point examination. 1, 2, 3

ACR Diagnostic Criteria

The ACR criteria focus on widespread pain and associated symptoms rather than specific laboratory or imaging findings 1:

• Chronic widespread pain must be present in all four body quadrants for a minimum of 3 months, characterized by hyperalgesia and allodynia 1
• History of widespread pain for 3 months, with pain present at 11 or more of the 18 specific tender point sites (1990 criteria) 2, 3
• The 2010 revised ACR criteria eliminated the tender point requirement and incorporated a broader symptom assessment, affecting approximately 5% of the population 4

Core Associated Symptoms Required

Beyond pain, the following symptoms strengthen the diagnosis and are part of the diagnostic framework 1:

• Fatigue that is disproportionate to activity level 1
• Non-restorative sleep or sleep disturbances 1, 5
• Cognitive dysfunction (often described as "fibro fog") 1, 5
• Mood disturbances, including anxiety and depression, are common but not required 1

Clinical Assessment Tools

• The Fibromyalgia Impact Questionnaire (FIQ) measures functional impairment and impact on daily activities, assessing pain, fatigue, sleep quality, and daily functioning 1, 3
• The Visual Analogue Scale (VAS) or numeric rating scale (0-10) assesses pain intensity, with baseline scores typically ≥4 required for clinical trials 2, 3
• The Fibromyalgia Rapid Screening Tool is helpful for screening patients with diffuse chronic pain 5

Laboratory Testing for Differential Diagnosis

Basic laboratory screening is used to exclude inflammatory or endocrine diseases, not to diagnose fibromyalgia 1:

• Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to exclude inflammatory conditions 1
• Thyroid function tests to rule out hypothyroidism 1
• Creatine kinase to exclude myopathies 1
• Vitamin D levels to rule out deficiency 1

Key Differential Diagnoses to Exclude

• Chronic fatigue syndrome may coexist or present similarly 1
• Post-Lyme disease syndrome can present with multiple tender points and widespread pain, fulfilling fibromyalgia criteria 1
• Systemic and rheumatic diseases must be ruled out by patient history, physical examination, and laboratory investigations 6
• Functional somatic syndromes (irritable bowel syndrome, migraine) and psychiatric diagnoses may be comorbid 5, 6

Clinical Context and Demographics

• Prevalence is approximately 2% in the general population, with higher prevalence in women (89% female in clinical populations) and increasing with age 7, 1, 5
• Predominantly affects women aged 30-60 years 1
• Diagnosis often takes over 2 years, with an average of 3.7 consultations with different physicians 7, 1

Important Diagnostic Pitfalls

• Fibromyalgia is not a diagnosis of exclusion—it has positive diagnostic criteria and should be diagnosed when criteria are met 8
• Tender points have limitations and are not required in modern diagnostic criteria; clinicians should be aware that the 1990 ACR classification criteria were designed for research, not individual patient diagnosis 6, 4
• Extensive laboratory tests and imaging are not required to diagnose fibromyalgia once basic screening excludes other conditions 4
• The condition is heterogeneous and complex, involving abnormal pain processing with multiple symptom domains 7