What are the guidelines to diagnose fibromyalgia?

Diagnosing Fibromyalgia

Fibromyalgia is diagnosed clinically based on chronic widespread pain lasting at least 3 months in all four body quadrants, accompanied by fatigue, sleep disturbances, and cognitive dysfunction, after excluding other organic diseases through targeted history, physical examination, and limited laboratory testing. 1, 2

Core Diagnostic Criteria

Primary Clinical Features Required

• Chronic widespread pain present in all four body quadrants for a minimum of 3 months, characterized by hyperalgesia (increased pain sensitivity) and allodynia (pain from normally non-painful stimuli) 1, 3
• Associated symptoms that strengthen the diagnosis include:
  • Fatigue disproportionate to activity level 1, 4
  • Non-restorative sleep 1, 5
  • Cognitive dysfunction (often described as "fibro fog") 1, 3
  • Mood disturbances including anxiety and depression 1, 3

American College of Rheumatology Criteria

The 1990 ACR classification criteria historically required pain at 11 or more of 18 specific tender point sites, but newer criteria no longer require tender point examination 2, 6. The 2016 criteria can be used to confirm clinical diagnosis after the comprehensive assessment 6.

Diagnostic Algorithm

Step 1: Screen for Chronic Widespread Pain

• Identify patients with pain in four of five body regions lasting at least 3 months 6
• Screen those with chronic widespread pain for unrefreshed sleep and fatigue 6

Step 2: Comprehensive Clinical Assessment

Fibromyalgia requires comprehensive assessment of pain intensity, functional limitations, sleep quality, fatigue severity, cognitive symptoms, and psychosocial factors including depression and anxiety 7, 2. This recognizes fibromyalgia as a complex condition with abnormal central pain processing (central sensitization) rather than peripheral tissue damage 2, 8.

Step 3: Exclude Organic Diseases

A complete medical history (including drug history) and complete physical examination is mandatory to consolidate the diagnosis or identify features pointing to other conditions 6. Limited laboratory screening is recommended to exclude inflammatory, endocrine, or rheumatic diseases 1, 6:

• Erythrocyte sedimentation rate (ESR) 1
• C-reactive protein (CRP) 1
• Thyroid function tests 1
• Creatine kinase 1
• Vitamin D levels 1

Step 4: Assess for Overlapping Conditions

Fibromyalgia as a stand-alone diagnosis is rare, as most patients meet criteria for other chronic overlapping pain conditions or mental disorders 6. Screen for:

• Chronic fatigue syndrome 1, 3
• Irritable bowel syndrome 3, 8
• Migraine 1, 3
• Temporomandibular disorder 8
• Primary mood disturbances requiring careful evaluation 3

Step 5: Functional Impact Assessment

Use the Fibromyalgia Impact Questionnaire (FIQ) to measure functional impairment and impact on daily activities, assessing pain, fatigue, sleep quality, and daily functioning 1. The Visual Analogue Scale (VAS) can assess pain intensity 1.

Critical Diagnostic Pitfalls to Avoid

• Do not rely solely on tender point examination: Clinicians should be aware of limitations inherent in using tender points for diagnosis 3, 6
• Do not order extensive laboratory testing: There are no specific laboratory tests for fibromyalgia; limit testing to basic screening to exclude other diseases 1, 3
• Do not miss psychiatric comorbidities: Numerous studies report higher prevalence of psychiatric disorders in fibromyalgia patients, requiring careful evaluation for primary mood disturbances 3
• Recognize diagnostic delays: Diagnosis often takes over 2 years with an average of 3.7 consultations with different physicians 1

Important Diagnostic Considerations

There is no "gold standard" for diagnosing fibromyalgia 3. All diagnostic criteria should be interpreted with caution, considered rudimentary, and subject to modification 3. The diagnosis requires that organic diseases are not causing the symptoms, making it essential to rule out systemic and rheumatic diseases through patient history, physical examination, and laboratory investigations 3.

Fibromyalgia represents abnormal central pain processing (central sensitization) with dysfunction of neuro-circuits involving perception, transmission, and processing of afferent nociceptive stimuli 2, 4, 8. The pathogenesis has been linked to inflammatory, immune, endocrine, genetic, and psychosocial factors 4.