MCP-1 and IL-8 as pain biomarkers in fibromyalgia: a pilot study.

Objective: Although fibromyalgia (FM) is traditionally a non-inflammatory condition, emerging data also suggest that FM has an immunologic component. Previous studies have reported that peripheral blood concentrations of two chemokines (i.e., interleukin-8 [IL-8] and monocyte chemotactic protein-1 [MCP-1]) were elevated in FM patients compared with normal controls. We sought to determine the longitudinal relationships of changes in the levels (picogram/mL) of IL-8 and MCP-1 with changes in the severity of FM-related pain.

Design: Secondary data analysis of a cohort of 16 FM subjects who provided blood samples at two time points: week 1 and week 12. Setting.  Urban rheumatology clinic practices.

Patients: Individuals who met the American College of Rheumatology 1990 criteria for FM.

Outcome Measures: Changes from week 1 to week 12 of the following variables: Brief Pain Inventory (BPI) pain severity and plasma concentrations of IL-8 and MCP-1.

Results:   Change in BPI pain severity was significantly associated with changes in IL-8 and MCP-1 plasma concentrations. Specifically, for each unit increase in the change of BPI pain severity, IL-8 increased by 2.5 pg/mL (P = 0.03) and MCP-1 increased by 9.4 pg/mL (P = 0.006). None of the covariates (i.e., body mass index, medications, severity of depression, and overall FM burden) were significantly associated with either chemokines.

Conclusion:   Although preliminary, our findings raise the hypothesis that IL-8 and MCP-1 may be involved in the pathogenesis of FM. If replicated in a larger study, IL-8 and MCP-1 may assist in determining prognosis and in monitoring of treatment response.