Simple method of circulating immune complex detection in human sera by polyethylene glycol precipitation

A rapid test for detection of circulating immune complexes in a small serum sample was developed to facilitate clinical diagnosis of immune complex disorders. The test is based on a selective precipitation of soluble circulating complexes of antigen-antibody in 3.75% concentration of high-molecular polyethylene glycol. Precipitation is followed photometrically at 450 nm, 1 cm cuv. after 1 h incubation at room temperature. Comparison of E450 values in groups of patients with immune complex disorders, such as rheumatoid arthritis, systemic lupus erythematosus and glomerulonephritis, with healthy controls or patients with non-immunological disorders revealed highly significant differences. Sera of all patients with high clinical activity of disease exhibited positive reaction. In 121 human sera the results of this examination were compared with the results of C 1 q binding test. There was 73.5% agreement between the results of both methods. Our test is more rapid, suited for routine clinical use.