Degradation products of fibrin and of fibrinogen in synovial fluid and in plasma of patients with rheumatoid arthritis

Degradation products of fibrin and of fibrinogen, together (FDP) and separately, were measured in plasma and synovial fluid of patients with rheumatoid arthritis using specific enzyme immunoassays. Considerable amounts of fibrin degradation products (fibrin-DP) were found in the synovial fluid; only 1 case yielded some fibrinogen-derived products (fibrinogen-DP). In plasma relatively small amounts of degradation products, both fibrin-DP and fibrinogen-DP, were present. From the discrepancy between the amount and composition of degradation products in synovial fluid and in plasma we conclude that there are extra-articular sites of fibrin(ogen) breakdown in rheumatoid arthritis. The new specific methods may contribute to the understanding of the role of fibrinolysis in rheumatoid disease and in inflammation in general.