The concept of incomplete fibromyalgia syndrome: comparison of incomplete fibromyalgia syndrome with fibromyalgia syndrome by 1990 ACR classification criteria and its implications for newer criteria and clinical practice.

BACKGROUND: The 1990 American College of Rheumatology (ACR) classification criteria for fibromyalgia/fibromyalgia syndrome (FMS) has 2 components: (a) widespread pain (WSP) and (b) presence of 11 or more tender points (TP) among possible 18 sites. Some clinic patients fulfill 1 component but not the other. We have considered these patients to have incomplete FMS (IFMS). The purpose of this study was to examine the clinical and psychological differences between IFMS and FMS (by 1990 ACR criteria) because such comparison may be helpful to diagnose patients in the clinic.
METHODS: Six hundred consecutive patients referred to our rheumatology clinic with a diagnosis of FMS were examined by a standard protocol to determine whether they fulfilled the 1990 criteria for FMS. Both IFMS and FMS groups were compared in demographic, clinical, and psychological variables using appropriate statistical methods.
RESULTS: One hundred twelve (18.7%) patients did not satisfy the 1990 ACR criteria and were classified as IFMS. Symptoms in IFMS and FMS were similar, generally with less frequent and less severe symptoms in the IFMS group. In IFMS, no significant difference was found among the WSP and TP component subgroups. Both TP and WSP were correlated with important features of FMS.
CONCLUSIONS: Fulfillment of the ACR 1990 criteria is not necessary for a diagnosis of FMS in the clinic. For diagnosis and management of FMS in the clinical setting, IFMS patients, along with consideration of the total clinical picture, may be considered to have FMS, albeit generally mild.