IL6 and rheumatoid arthritis: In RA SF, IL-6 concentrations (354.7 (1,851.6) pg/ml) were threefold higher than in the OA samples (119.4 (193.2) pg/ml; P < 0.05), and they were fourfold higher than in the asymptomatic organ donor samples (86.97 (82.0) pg/ml; P < 0.05).