Determination of the apparent synovial permeability in the knee joint of patients suffering from osteoarthritis and rheumatoid arthritis.

The concentrations of alpha 1-acid glycoprotein (alpha 1-antitrypsin (alpha 1-AT), ceruloplasmin (Cp) and alpha 2-macroglobulin (alpha 2-MG) in serum and in knee joint synovial fluid of patients suffering from rheumatoid arthritis (RA) and osteoarthritis (OA) were determined and apparent synovial permeability (SP) to each protein calculated. The results showed that the rheumatoid synovia were significantly more permeable (P < 0.001) than the osteoarthritic synovia. Cp and alpha 2-MG showed the greatest average increase in apparent SP, about five times the values for OA joints. Apparent SP reflected disease activity rather well, since the patients with the more active disease had the highest values, six times that of the OA values. Although the values for the small proteins alpha 1-AGP and alpha 1-AT were greater in RA joints, more intense inflammation resulted in a greater increase in apparent SP to larger proteins, so that the apparent SP for alpha 2-MG and Cp are more reliable for evaluating disease activity. Apparent SP as determined by this and previous studies appeared to be a much more accurate and sensitive measure than the synovial fluid/plasma protein concentration ratio. Knowledge of the apparent SP could be a useful parameter in evaluating synovitis since the exudative flare-ups usually parallel the intensity of the inflammation.