IgG Rheumatoid Factor in Synovial Fluid of Patients with Rheumatoid Arthritis.

We measured IgG-RF in the synovial fluid of 34 patients (39 joints) with rheumatoid arthritis (RA) by enzyme immunoassay. As a control group we measured IgG-RF in the synovial fluid of 20 patients (22 joints) with osteoarthrosis and hydroarthrosis. We measured IgG-RF in the synovial fluid of non RA patients consisting of one patient (one joint) with gout arthritis, one patient (one joint) with pseudo gout and 2 patients (2 joints) with monoarthritis. The IgG-RF titer in the synovial fluid from RA patients was significantly higher compared to the control group and non RA patients. There was a significant correlation in the IgG-RF in the synovial fluid, between stage 1 and 2, 1 and 3, in the X-ray staging of the joint that was aspirated. The IgG-RF titer was high, above 2.0, in almost all cases of stage 2 and 3 on X-ray and demonstrated high activity. These results suggest a correlation between IgG-RF in the synovial fluid of RA patients and radiologic progression.