Hidden Rheumatoid-Factor In Active Seronegative Rheumatoid Arthritis

Four of 21 patients with active, longstanding rheumatoid arthritis were shown to have hidden rheumatoid factor, by means of Sephadex fractionation at neutral pH. The phenomenon is probably due to antigen-antibody type interaction between IgM rheumatoid factor and autologous native 7S gamma-globulin. The presence of hidden rheumatoid factor should be considered in clinical studies of rheumatoid disease, where subdivision in seropositive and seronegative groups is used. Folke D. Lindström Department of Rheumatology University Hospital Lund Sweden