Trace Element Concentrations in Synovial Fluid of Rheumatoid Arthritis and Osteoarthritis and its Multivariate Analysis

Shunsuke Meshitsuka, Youichi Kurozawa, Kazuhiko Funakawa, Nobuo Iwai, Hitoshi Ohshiro and Takayuki Nose

Department of Public Health, Faculty of Medicine, Tottori University, Yonago 683, Japan

The mean concentrations of Zn, Fe, Cu, Mg, Ca, Mn, Cd, Cr and Au in synovial fluid of knee joints of patients with rheumatoid arthritis, osteoarthritis and other joint diseases were measured. The value of the Cu concentration in rheumatoid arthritis (0.80 µg/mL) was higher than that in osteoarthritis (0.49 µg/mL) (P < 0.001). The concentration of Zn in rheumatoid arthritis (0.57 µg/mL) was higher than that in osteoarthritis (0.35 µg/mL) (P < 0.01). The Mg concentration was also higher in rheumatoid arthritis than in osteoarthritis (P < 0.05). Au concentration in synovial fluid (0.13 µg/mL) was higher than that in plasma, suggesting that Au may accumulate in synovial fluid. In rheumatoid arthritis Cu, Zn and Mg were highly correlated. In the multiple regression analysis, the erythrocyte sedimentation rate and CRP were explained 76% and 72% by the concentrations of the metal ions, respectively. The trace elements may not directly play roles in the etiology of rheumatoid arthritis, but the types of inflammatory effusions may be expressed in the trace element concentrations in synovial fluid. In the discriminant analysis using the concentrations of Cu, Zn, Mg and Mn, the sensitivity and specificity of the screening for the diagnosis of rheumatoid arthritis were 71% and 86%, respectively. The discriminant analysis of Cu, Zn, Mg and Mn is shown to be beneficial for the diagnosis.

Key words: metal concentration; osteoarthritis; rheumatoid arthritis; synovial fluid

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