Prevalence of the fibromyalgia phenotype in patients with spine pain presenting to a tertiary care pain clinic and the potential treatment implications.

OBJECTIVE: Injections for spinal pain have high failure rates, emphasizing the importance of patient selection. It is possible that detecting the presence of a fibromyalgia (FM)-like phenotype could aid in prediction, because in these individuals a peripheral injection would not address pain due to alterations in central neurotransmission. We undertook this study to test the hypothesis that patients who have spine pain meeting survey criteria for FM would be phenotypically distinct from those who do not.

METHODS: We studied 548 patients diagnosed as having primary spine pain. All patients completed validated self-report questionnaires, including the Brief Pain Inventory, the PainDETECT questionnaire, the Hospital Anxiety and Depression Scale, measures of physical function, and the FM criteria and severity scales.

RESULTS: Forty-two percent of the patients were FM positive according to the FM criteria and severity scales. Compared with FM-negative patients, FM-positive patients were more likely to be younger, unemployed, and receiving compensation for pain and to have greater pain severity and pain interference and more neuropathic pain descriptors as well as higher levels of depression and anxiety and a lower level of physical function (P < 0.002 for each comparison). Female sex, neuropathic pain, pain interference, and anxiety were independently predictive of FM status in a multivariate analysis (P < 0.01 for all variables). Receiver operating characteristic curve analysis showed a strength of association of 0.80 as measured by the cross-validated C statistic.

CONCLUSION: Using the FM criteria and severity scales, we demonstrated profound phenotypic differences in a population of patients with spine pain. Although centralized pain cannot be confirmed with a self-report instrument alone, the pathophysiology of FM may help explain a portion of the variability of responses to spine interventions.