Widespread pain is no longer required for fibromyalgia (FM) diagnosis according to the American College of Rheumatology (ACR) 2010 preliminary diagnostic criteria and its 2011 modification, but its absence may be of concern. We investigated whether the widespread pain definition was satisfactory and the consequences of having a small number of painful regions or of not satisfying the widespread pain criterion.
We studied 5011 patients who satisfied the 2011 criteria. FM was identified using the Widespread Pain Index (WPI) and the Symptom Severity Scale (SSS): WPI ≥ 7 and SSS ≥ 5 or WPI 3-6 and SSS ≥ 9. Widespread pain was 4 quadrants plus axial pain, according to the 1990 ACR FM criteria.
There were 4700 patients (93.8%) who satisfied the ACR 1990 widespread pain criterion. Using a new strict definition for 5 pain regions based on the WPI sites, a modified widespread pain criterion requiring 4 of 5 regions identified 98.8% of criteria-positive patients. Patients without widespread pain or those in the low WPI/high SSS group had milder FM and no evidence of increased psychological or physical distress.
In usual clinical and epidemiological studies, the 2011 and 2010 criteria work well, but are not as effective in patients with asymmetrical or regional pain who do not satisfy a widespread pain criterion. A ≥ 4-pain region widespread pain definition will eliminate regional pain false-positives and will identify 98.8% of current 2011 cases. Future revisions of the 2010/2011 criteria should consider incorporating the ≥ 4-region requirement to avoid misclassification.