A rapid, sensitive and specific radioimmunoassay for human chorionic gonadotrophin.

A specific, quantitative assay for human chorionic gonadotrophin (hCG) in plasma has been developed using an hCG-beta antiserum and an assay procedure lasting four hours. It employs a double antibody method and in a procedure prior to assay the two antibodies are pre-incubated in bulk and then stored in ampoules in lyophilised form ready for use. The assay procedure is a dis-equilibrium (sequential saturation) system in which the sample or unlabelled antigen is first incubated with the pre-incubated antisera followed by the addition of the labelled antigen and a further incubation. The antigen-antibody complex is separated from free antigen by vacuum filtration on glass fibre discs. The assay sensitivity is 100-200 picograms hCG/ml (0.68 mIU/ml) and is uninfluenced by normal concentrations of luteinising hormone in the sample.