Free-radical oxidation (peroxidation) products in serum and synovial fluid in rheumatoid arthritis.

Free-radical oxidation (peroxidation) products were measured in (a) 65 synovial effusions and (b) 30 sera from normal subjects and 58 sera from patients with rheumatoid arthritis (RA). Free-radical oxidation products were detectable in 90% of synovial fluids, their concentration being higher in "inflammatory" than in "degenerative" joint disease. Free-radical oxidation products in serum were significantly elevated in patients with RA compared to normal controls; the levels declined after treatment with a variety of antiinflammatory agents.