Double-antibody enzyme immunoassay applied to human alpha 1-fetoprotein

We report the development of a double-antibody system for enzyme immunoassay of human alpha 1-fetoprotein. Equilibrium and sequential saturation procedures were evaluated and compared with a similar double-antibody radioimmunoassay. With our method, 3 mug of alpha 1-fetoprotein per liter can be detected. The dose-response curve covers a 100-fold range of analyte concentrations. Within-run and between-run coefficients of variation are respectively 6.9% and 10.0%. Analytical recovery of added antigen is 99.5 +/- 10.6%. Results are routinely obtained in 24 h but can be obtained in less than 8 h. Alpha 1-fetoprotein was measured in a variety of clinical samples, including sera from 488 pregnant women. The advantages of the present method over radioimmunoassay and other enzyme immunoassay procedures are discussed.