Preliminary criteria for primary fibromyalgia syndrome (PFS): multivariate analysis of a consecutive series of PFS, other pain patients, and normal subjects.

Primary fibromyalgia syndrome (PFS) is a common form of nonarticular rheumatism with chronic and generalized musculoskeletal aching and stiffness, accompanied by tender points at characteristic sites in the absence of an underlying condition. No satisfactory criteria for its diagnosis, based on appropriate controlled studies, have yet been proposed. We undertook such a study which included a consecutive series of clinically diagnosed PFS and compared them with 3 control groups--mild rheumatoid arthritis, localized fibromyalgia secondary to trauma and normal controls. Multivariate statistical analysis plus clinical judgement identified 6 historical features and 7 pairs of tender points that best discriminated PFS from the control groups. The criteria, derived from a combination of these historical features and tender points, provided greater than 90% sensitivity and specificity. In an independent and consecutive sample of 45 PFS patients, the criteria yielded a sensitivity of 89%. The present study indicates that a combination of historical features and TP's will likely provide effective PFS criteria.