[C-reactive protein in inflammatory articular diseases: comparison of concentrations in blood and synovial fluid]

We evaluated the diagnostic value of measuring C-Reactive Protein (CRP) in blood and in synovial fluid for the detection of inflammatory articular diseases in 154 patients. High concentrations of CRP in blood were found in microcrystalin arthritis, polymyalgia rheumatica and Horton's disease. Our results show a good correlation between CRP and erythrocyte sedimentation rate for ankylosing spondylitis (p less than 0.01), systemic lupus erythematosus (p less than 0.01), rheumatoid arthritis (p less than 0.05), polymyalgia rheumatica and Horton's disease (p less than 0.05). The CRP measurement in blood did not separate seropositive versus seronegative rheumatoid arthritis, systemic lupus erythematosus versus rheumatoid arthritis and treated versus non-treated rheumatoid arthritis. There was a good correlation between CRP concentration in blood and in synovial fluid but the concentration was lower in synovial fluid than in blood (p less than 0.01). Then, the CRP measurement in synovial fluid does not have a higher diagnostic value than in blood.