Some characteristics of the double antibody method for the assay of gonadotropins.

Some characteristics of the double antibody method for the assay of gonadotropins are discussed. Radioimmunoassay (RIA) methods differ primarily in the method used in the separation of that portion of labeled Ag which is bound to Ab from that portion which is free. Methods of separating bound and free labeled Ag include precipitation of Ag-Ab soluble complexes differential migration of bound and free antigen and adsorption of the free antigen. Some of the serum factors responsible for nonspecific effects include protein concentration euglobulin fraction thermolabile fraction enzymes lipid content and complement. The effects of nonspecific interfering factors may be minimized by heating storage before use dialysis sample dilution use of plasma heparin antigen-free serum or trasylol fasting sample a well buffered system and EDTA. Urinary factors contributing to nonspecific effects include pH urea concentration ionic strength protein concentration and salt concentration. The application of the double antibody assay method and the influence of these factors is discussed. Although keen attention is required in the application of this method it has the following advantages: 1) possibility of application to any available Ag and to any labeled Ag 2) possibility of application without reviewing established conditions for 1 antiserum obtained in the same species 3) interference from preexisting damaged radioactive Ag is relatively small and 4) versatility and low cost.