Interleukin-6 levels in serum and synovial fluid in patients with arthritis

Objective To compare the interleukin-6(IL-6) levels in patients with variety of arthritides and to evaluate the significance of IL-6 in the onset of rheumatoid arthritis(RA) and the correlation between IL-6 and RA disease activity. Methods The IL-6 levels in serum and synovial fluid in patients with RA, ankylosing spondylitis(AS), osteoarthritis(OA), and gouty arthritis were measured by radioimmunoassay, and the correlation between IL-6 and RA disease activity indicators was analyzed. Results The IL-6 levels both in serum and synovial fluid in RA patients was significantly higher than that in other kinds of arthritic patients, and the level of IL-6 in synovial fluid was significantly higher than that in serum in patients with RA. There were significant positive correlations between IL-6 level in serum and tender joint count, swollen joint count, and CRP as well as between IL-6 level in synovial fluid and pain joint count, tender joint count, swollen joint count, ESR, and CRP in patients with RA. Conclusion IL-6 is involved in the onset of RA and the determination of its level both in synovial fluid and serum in patients with RA is helpful for diagnosis of RA and estimating its disease activity.