Background/Purpose: Fibromyalgia (FM) is a chronic disease characterized by severe, long lasting pain that spreads widely in almost whole body. The cause of the disease is still unknown, and no efficient treatment has yet been established. It is well known that the severity of pain as well as accompanying symptoms can often be influenced either by psychological or by social factors, which support the recognition of the disease as one of functional somatic disorders.

Methods: American College of Rheumatology (ACR) revised the classification criteria for diagnosis of FM in 2010, after 20 years of clinical use of the old one that had been published in 1990. Old criteria simply classifies patients as FM by number of tender points (11 or more, out of 18 in total), whereas new one considers not only the extent of widespread pain but also the severity of pain and many accompanying symptoms. In this study, comparison between the new and old criterion was performed in total 61 patients with FM or doubtful FM (male 11, female 50, average age 54.0 years, average duration from onset 4.5 years).

Results: Tender points by 1990 criteria was 12.0 in average (min 0, max 18), with 42 patients out of 56 presenting 11 or more, who were diagnosed as FM. Average Widespread Pain Index (WPI) and Symptom Severity (SS) by 2010 criteria scored 10.9 (min 2, max 18) and 6.1 (min 1, max 12), respectively, resulting 38 out of 59 were diagnosed as FM (WPI>7, SS>5 or 3<WPI<6, SS>9). Sum of the two scores in new criteria, WPI and SS, was 16.8 in average (min 3, max 29), and demonstrated positive correlation with tender points in old criteria (r=0.45). However, diagnoses by the two criterion did not always coincide.

Conclusion: Despite of overall accordance between two criterions, the diagnosis did not always coincide. Interestingly, the positivity of tender points in old criteria as well as that of widespread pain in new one demonstrated significant differences by the locus. Moreover, the positivity of accompanying symptoms in new criteria (41 in total) demonstrated significant differences from each other. All these differences may suggest that pain and tender locus as well as accompanying symptoms could be weighed either more or less, not equally as they are, depending the influence in diagnosis. Physicians should apply these criterion flexibly.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparison-of-new-and-old-american-college-of-rheumatology-classification-criterion-for-diagnosis-of-fibromyalgia/