Heterogeneity Within the Fibromyalgia Population: Theoretical Implications of Variable Tender Point Severity Ratings

Objective. The American College of Rheumatology (ACR) tender point (TP) criterion is used in diagnosing fibromyalgia syndrome (FM). There has been little research investigating patterns of positive TP. We investigated response patterns of TP in a sample of patients with FM. Methods. Manila I TP survey data were available oil 1433 patients with FM. Factor analysis was conducted oil ACR TP and control (CON) points. Factor scores were Cluster analyzed to identify subgroups based on TP scores. Subgroups were compared oil demographic and psychosocial variables. Results. Factor analysis resulted in 4 TP groupings: neck/shoulder girdle, gluteal/trochanteric, and tipper extremity regions, and a set of CON TP. Cluster analysis revealed 3 Clusters. Group 1 was high on all 3 TP regions and the CON set; Group 2 moderate on the 3 TP regions, low oil the CON set; and Group 3 was relatively low on all 3 TP regions and the CON set. The group highest oil the CON and TP regions reported the greatest pain (7.58 +/- 1.23; p < 0.001), sleep disturbance (7.05 +/- 1.61; p < 0.001). anxiety (10.14 +/- 4.57; p < 0.001), and depression (8.42 +/- 4.4; p < 0.001). Conclusion. TP severity ratings varied among cluster groups, suggesting patients with FM are not homogeneous. Variations in TP severity provide information regarding the degree to which FM affects patients' quality of life. Patients with elevated scores oil the CON TP demonstrated a genera] pattern reflecting lower thresholds for symptom reporting and, perhaps, disease severity. Research is needed to elucidate mechanisms underlying heterogeneity among the FM population. (First Release Nov 15 2009; J Rheumatol 2009;36:2795-801; doi: 10.3899/jrheum.090432)