What are the diagnostic criteria and tests for fibromyalgia?

Diagnostic Criteria and Tests for Fibromyalgia

Fibromyalgia is diagnosed primarily through clinical assessment using established diagnostic criteria, with no single definitive laboratory or imaging test available for confirmation. 1

Diagnostic Criteria

American College of Rheumatology (ACR) Criteria

• Traditional 1990 ACR Criteria:

  • History of widespread pain present for at least 3 months
  • Pain upon digital pressure (approximately 4 kg of pressure) in at least 11 of 18 specific tender points
  • The 18 tender points are distributed symmetrically across the body 1

• Updated ACR Criteria:

  • Moved away from tender point examination toward symptom assessment
  • Focus on widespread pain index (WPI) and symptom severity scale (SS)
  • Accounts for associated symptoms like fatigue, cognitive symptoms, and sleep disturbances 1, 2

Tender Point Locations (18 sites)

• Bilateral points at:
  • Occipital region
  • Cervical spine
  • Trapezius muscle
  • Supraspinatus muscle
  • Second rib (costochondral junction)
  • Lateral epicondyle
  • Gluteal region
  • Greater trochanter
  • Knee (medial fat pad) 1

Diagnostic Approach

Step 1: Clinical Assessment

• Pain Assessment:

  • Document pain that is:
    • Widespread (affecting all four quadrants of the body)
    • Present for at least 3 months
    • Not explained by another condition 1, 3

• Associated Symptoms Evaluation:

  • Fatigue
  • Sleep disturbances
  • Cognitive dysfunction ("fibro fog")
  • Mood disturbances (anxiety, depression)
  • Headaches
  • Irritable bowel symptoms
  • Urinary frequency 1, 4

Step 2: Screening Tools

• Fibromyalgia Rapid Screening Tool (FiRST):

  • Quick screening method for patients with diffuse chronic pain 3

• Fibromyalgia Survey Questionnaire (FSQ):

  • Self-report questionnaire that can assist physician diagnosis 2

Step 3: Laboratory Testing

• Purpose: To exclude other conditions, not to confirm fibromyalgia
• Basic laboratory tests to consider:
  • Complete blood count
  • Erythrocyte sedimentation rate
  • C-reactive protein
  • Thyroid function tests
  • Creatine kinase
  • Vitamin D levels 1, 2

Step 4: Differential Diagnosis

• Rule out conditions with similar presentations:
  • Inflammatory rheumatic diseases
  • Hypothyroidism
  • Myopathies
  • Multiple sclerosis
  • Other pain syndromes 2

Common Pitfalls in Diagnosis

• Overreliance on tender points: The updated criteria place less emphasis on tender point examination and more on symptom assessment 2

• Excessive testing: Once clinical criteria are met and basic testing excludes other conditions, additional tests are rarely helpful and may increase patient anxiety 1, 2

• Delayed diagnosis: Many patients receive incorrect diagnoses of food allergies, celiac disease, asthma, or bronchitis before fibromyalgia is recognized, leading to unnecessary tests and treatments 5

• Failure to recognize comorbidities: Fibromyalgia often coexists with other conditions including:

  • Functional somatic syndromes
  • Psychiatric disorders
  • Inflammatory rheumatic diseases 3

Special Considerations

• Gender differences: Fibromyalgia is diagnosed more frequently in women, but presentation may differ in men 3

• Age considerations: Symptoms and presentation may vary with age 1

• Comorbid conditions: Presence of other rheumatologic or psychiatric conditions may complicate diagnosis 1, 3

When to Refer

• Refer to a rheumatologist when:

  • Diagnosis remains uncertain
  • Inflammatory rheumatic disease is suspected
  • Standard management approaches have failed 2

• Refer to mental health specialists when:

  • Significant psychiatric comorbidities are present
  • Psychological factors significantly impact symptom severity 1, 2

By following these diagnostic criteria and testing approaches, clinicians can accurately diagnose fibromyalgia, avoid unnecessary testing, and develop appropriate treatment plans focused on improving function and quality of life.