Pain, disability, and physical functioning in subgroups of patients with fibromyalgia.

OBJECTIVE: To investigate (1) whether patients with fibromyalgia (FM) could be subgrouped on the basis of psychosocial and behavioral responses to pain, and (2) the relationships among pain severity, perceived disability, and observed physical functioning, as measured by cervical spinal mobility.

METHODS: 117 patients with FM received a comprehensive examination, underwent physical performance tasks during the evaluation, and completed self-report inventories.

RESULTS: About 87% of the patients could be classified into the Multidimensional Pain Inventory clustering groups identified and validated in patients with a range of chronic pain problems (Dysfunctional, Interpersonally Distressed, and Adaptive Copers). Although the 3 groups exhibited comparable levels of physical functioning, the Dysfunctional and Interpersonally Distressed patients reported higher levels of pain, disability, and depression. Interpersonally Distressed patients also reported significantly lower levels of marital satisfaction than the other 2 subgroups. There were significant associations between pain severity and perceived disability, and pain severity and physical functioning, defined by spinal mobility tests. The relationship between disability and physical functioning did not reach statistical significance. Correlational analyses by subgroups revealed a significant association between patient perceived disability and physical functioning in the Adaptive Copers, but not the Dysfunctional or Interpersonally Distressed patients.

CONCLUSIONS: Patients with FM can be classified into 3 subgroups based on psychosocial and behavioral characteristics. These subgroups show substantial differences in clinical presentation of their symptoms. Although the results should be considered preliminary due to the narrow range of physical functioning, the differential relationships between perceived disability and physical functioning across cluster groups suggest the importance of FM syndrome as a heterogeneous disorder. Treating patients with FM as a homogeneous group may compromise research results, impede understanding of the mechanisms underlying this condition, and deter development of effective treatment.