Objective: Monocyte chemoattractant protein 1 (MCP-1) level in plasma is described as a marker for joint inflammation in rheumatoid arthritis (RA).
Methods: MCP-1 in plasma and synovial fluid (SF) was quantified by ELISA in 36 RA patients with synovitis of the knee at Day 1 and 30. Disease activity was assessed by the swollen joint count, Ritchie Articular Index (RAI), global assessment, pain on visual analog scale, Health Assessment Questionnaire, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP).
Results: By linear regression analysis plasma MCP-1 levels correlated significantly with the swollen joint count (Day 1: R = 0.47, p = 0.005; Day 30: R = 0.53, p < 0.001) and the RAI (Day 1: R = 0.37, p = 0.03; Day 30: R = 0.41, p = 0.01). The correlations of swollen joint count and RAI with ESR and CRP were significant only on Day 30 for the ESR (R = 0.40, p = 0.02). No association was found between plasma MCP-1 levels and the ESR/CRP levels. MCP-1 levels in plasma in RA patients were elevated compared to controls (p < 0.001) and MCP-I levels in SF were higher than in plasma (p < 0.001). No correlation was found between SF MCP-1 levels and in vitro migration of mononuclear cells towards SF. MCP-1 appears to participate in the disease process in RA, and plasma MCP-1 may be useful in monitoring joint inflammation.