Fibromyalgia (FM) is a chronic pain disorder characterized by widespread pain, fatigue, sleep disturbances, cognitive dysfunction, and somatic symptoms. Over the past three decades, the American College of Rheumatology (ACR) has revised its classification criteria multiple times to reflect evolving understanding of FM pathophysiology, symptom spectrum, and clinical presentation. This article reviews each major version of the ACR criteria—1990, 2010, and 2016—providing practical guidance for medical doctors applying these frameworks in clinical practice.

1. Background

Fibromyalgia is not diagnosed via laboratory tests or imaging. Instead, it is a clinical diagnosis rooted in symptom patterns and exclusion of mimicking conditions. The evolution of classification criteria reflects shifts in clinical emphasis:

• 1990 ACR Criteria: Emphasized tender point examination, reflecting a focus on peripheral pain sensitivity.
• 2010 ACR Criteria: Shifted to a symptom-based approach using patient-reported outcomes.
• 2016 ACR Revisions: Refined and clarified the 2010 criteria, incorporating widespread pain distribution and adjusting scoring thresholds.

Together, these criteria guide both clinical diagnosis and research standardization.

2. ACR 1990 Criteria

The ACR 1990 criteria were the first formal attempt to classify fibromyalgia for research and clinical purposes. They remain widely referenced but are less commonly used today.

Requirements

A patient meets the 1990 criteria if both are present:

1. Widespread Pain

• Present for ≥3 months
• Defined as:
  • Pain on both left and right sides of the body
  • Pain above and below the waist
  • Axial pain (cervical spine, anterior chest, thoracic spine, or low back)

2. Tender Point Examination

• ≥11 out of 18 tender points positive on digital palpation
• Pressure of ~4 kg needed to elicit pain
• Tender points located in classic regions such as occiput, trapezius, supraspinatus, gluteal, greater trochanter, and knees

Strengths

• Provided standardized physical criteria
• Useful for research consistency

Limitations

• Tender point exam is subjective and difficult to reproduce reliably
• Tender points influenced by mood, anxiety, and examiner technique
• Does not incorporate fatigue, sleep disturbance, or cognitive symptoms

Because of these limitations, reliance on tender points declined, prompting development of new criteria.

3. ACR 2010 Criteria

The ACR 2010 criteria represented a major shift: diagnosis based on symptom severity rather than tender points. These criteria introduced two key scoring systems:

• Widespread Pain Index (WPI): Count of painful body regions (0–19)
• Symptom Severity Scale (SSS): Severity of fatigue, unrefreshing sleep, cognitive symptoms (0–9), plus somatic symptom burden (0–3)
  Total SSS score: 0–12

Diagnostic Requirements (2010)

Fibromyalgia can be classified when:

1. WPI ≥7 AND SSS ≥5
   OR
   WPI 3–6 AND SSS ≥9

AND

2. Symptoms present at a similar level for ≥3 months

AND

3. No other disorder that would otherwise explain the pain

Advantages

• No tender point examination required
• Includes key fibromyalgia symptoms: fatigue, sleep disturbance, cognitive impairment
• More reflective of real-world clinical presentations

Drawbacks

• No explicit requirement for pain distribution (later corrected in 2016)
• Potential for overdiagnosis in patients with widespread symptoms due to comorbidities

4. ACR 2016 Revision

The 2016 revisions corrected limitations of the 2010 criteria, enhanced specificity, and clarified diagnostic rules. These are now the preferred criteria for both clinical and research use.

Key Components

Fibromyalgia is diagnosed when all three conditions are met:

Condition 1: Symptom Scores

One of the following:

• WPI ≥7 AND SSS ≥5
  OR
• WPI 4–6 AND SSS ≥9

(Same scoring thresholds as 2010.)

Condition 2: Generalized Pain

Pain must be present in at least 4 of 5 regions:

1. Left upper region
2. Right upper region
3. Left lower region
4. Right lower region
5. Axial region

Jaw, chest, and abdominal pain are excluded from the regional count.

This addressed prior criticisms about insufficient emphasis on widespread pain distribution.

Condition 3: Duration

Symptoms must be present for ≥3 months.

Additional Notes and Clarifications (2016)

• The diagnosis of FM is valid regardless of other comorbidities (e.g., rheumatoid arthritis, lupus) if criteria are met.
• Fibromyalgia classification is not solely a diagnosis of exclusion but clinicians must reasonably rule out alternative explanations for widespread pain.
• The tender point exam remains optional and not part of the official criteria.

5. Comparing the Criteria

6. Practical Application in Clinical Practice

Clinical Steps for Diagnosis

1. History and symptom assessment
   • Pain pattern, fatigue, sleep, cognitive symptoms
   • Apply WPI and SSS scoring
2. Rule out alternative diseases
   • Hypothyroidism, inflammatory arthritis, myopathies, vitamin D deficiency
   • Labs: CBC, ESR/CRP, TSH, CK—typically normal in FM
3. Assess generalized pain distribution
   • Use the 2016 regional mapping
4. Consider associated features
   • IBS, interstitial cystitis, migraine, TMJ dysfunction
   • Not required but common in FM spectrum disorders
5. Provide diagnosis and education
   • Emphasize neurobiological rather than structural pathology
   • Address management strategies: exercise, CBT, sleep hygiene, pharmacotherapy

7. Conclusion

The evolution of ACR fibromyalgia criteria reflects an improved understanding of FM as a centralized pain disorder with multifaceted symptomatology. The 2016 ACR criteria currently provide the most comprehensive and practical framework, incorporating both symptom severity and pain distribution while eliminating reliance on tender point examination.

For clinicians, accurate application of these criteria helps ensure appropriate diagnosis, supports clearer patient communication, and facilitates evidence-based management. As emerging research continues to clarify mechanisms of central sensitization, future revisions may further refine diagnostic pathways.