A rapid micro-modification of the quantitative immunoprecipitation assay.

A micro-modification of the quantitative immunoprecipitin test is described which permits rapid and sensitive titering of antisera, or quantitation of antigen, within a few hours. The procedure requires less than a microgram of radiolabeled antigen and can be used to titer antisera containing less than 1 microgram/ml of precipitating antibody. Radiotiters obtained for commercial antisera agree closely with results obtained using the classical quantitative immunoprecipitation procedure. The radiotiter assay procedure has been adapted for quantitating albumin in human urine by radioimmunoassay. The analysis can be performed in approximately 1 h, is sensitive to less than 50 ng of albumin, and requires no special apparatus or separation techniques.