What was the major advance of the 2010 criteria over the 1990 ACR criteria?▼
The 1990 ACR criteria required a physician to perform a specialized tender point examination at 18 specific anatomical sites using a pressure of approximately 4 kg. A patient needed 11 or more positive sites combined with widespread pain present for at least 3 months. This approach had significant problems: many clinicians were not trained in the examination, inter-rater reliability was poor, the criteria missed the extensive non-pain symptom burden of fibromyalgia (fatigue, cognitive dysfunction, sleep disturbance), and men were systematically underdiagnosed because of higher pain thresholds requiring more pressure. The 2010 criteria replaced the physical examination with the Widespread Pain Index and Symptom Severity Scale - tools that can be administered by interview or self-report, capture the full symptom picture of fibromyalgia, and correctly classified 88.1% of cases classified by the ACR 1990 criteria, without a tender point or physical examination.
How is the Symptom Severity Scale (SSS) Part B scored in clinical practice?▼
Part B of the SSS reflects the physician's estimate of the overall somatic symptom burden based on reviewing a list of 41 possible somatic symptoms: headache, pain or cramps in lower abdomen, irritable bowel syndrome, fatigue/tiredness, thinking or remembering problems, muscle weakness, headaches, pain or cramps in the abdomen, numbness/tingling, dizziness, insomnia, depression, constipation, pain in the upper abdomen, nausea, nervousness, chest pain, blurred vision, fever, diarrhea, dry mouth, itching, wheezing, Raynaud's phenomenon, hives/welts, ringing in ears, vomiting, heartburn, oral ulcers, loss/change in taste, seizures, dry eyes, shortness of breath, loss of appetite, rash, sun sensitivity, hearing difficulties, easy bruising, hair loss, frequent urination, painful urination, and bladder spasms. The clinician assigns: 0 = no symptoms, 1 = few symptoms (1-10), 2 = a moderate number (11-24), 3 = a great deal (25 or more).
What is the Fibromyalgia Severity (FS) score and how is it used?▼
The FS score is simply the sum of WPI and SSS (0-31 total). It serves as a continuous measure of fibromyalgia symptom burden that can be used to track treatment response over time. A patient classified as fibromyalgia at one visit may have a lower FS score at the next visit if treatment is effective - even if they still technically meet criteria. It is also useful for patients who have had fibromyalgia in the past but whose current symptoms may be below the classification threshold: the FS scale can still quantify their ongoing symptoms. General interpretive guidelines: 0-12 mild, 13-19 moderate, 20-31 severe, though these bands were not formally derived and clinicians should track change from baseline rather than use fixed categories.
Why does Option B of the criteria allow a lower WPI if the SSS is very high?▼
The two-pathway structure (Option A: WPI≥7+SSS≥5; Option B: WPI 3-6+SSS≥9) reflects the clinical reality that fibromyalgia is not a purely pain-distribution disorder. Some patients with fibromyalgia have intense systemic symptom burden - profound fatigue, severely disrupted sleep, significant cognitive impairment, and numerous somatic symptoms - but may not report widespread pain in as many body regions as other patients. These patients have the same underlying centralized nervous system sensitization but express it more prominently through symptom severity than pain distribution. Option B captures them by requiring the same overall fibromyalgia severity threshold but with different weighting between WPI and SSS components.
Can a patient with another diagnosis (e.g., RA or lupus) also be classified as having fibromyalgia?▼
Yes - one of the important features of the 2010 criteria was the explicit statement that fibromyalgia can coexist with other diagnoses. The 2010 criteria removed the previous exclusion criterion that required the pain not to be explained by another disorder. This is clinically crucial because up to 20-30% of patients with rheumatoid arthritis, lupus, ankylosing spondylitis, and other inflammatory conditions also meet fibromyalgia criteria. In these patients, the fibromyalgia component explains why disease activity scores remain high despite effective anti-inflammatory therapy, why pain persists despite disease remission, and why fatigue and sleep disturbance are disproportionate to disease activity. Recognizing concurrent fibromyalgia prevents over-treatment with immunosuppressants and allows appropriate multimodal fibromyalgia management.
What are the main limitations of the 2010 criteria?▼
The most important limitation of the 2010 criteria is the risk of misclassifying regional pain syndromes as fibromyalgia. A patient with severe localized pain in multiple areas (e.g., both shoulders from rotator cuff pathology, both knees from osteoarthritis, and low back pain) could generate a WPI of 7+ without having the centralized, widespread pain that defines fibromyalgia. This problem motivated the 2016 revision, which added a generalized pain requirement (pain in 4 of 5 body regions, excluding jaw, chest, and abdomen). Other limitations include: the somatic symptom burden scoring (Part B) is inherently physician-dependent and subjective; the criteria were developed largely in specialized rheumatology populations and may over-classify in primary care; and the criteria do not distinguish fibromyalgia from other centralized pain disorders such as chronic widespread pain.