Magnetisable solid-phase separation fluoroimmunoassay for total oestriol in pregnancy serum.

A rapid separation fluoroimmunoassay for serum or plasma levels of total oestriol in pregnancy was established, based on the use of fluorescein-labelled oestriol and sheep anti-oestriol serum covalently linked to magnetisable particles. Equilibrium was attained within 10 min, and the fluorescence of the bound fraction of labelled ligand was quantitated fluorimetrically after elution from the magnetisable particles. Results for pregnancy serum samples correlated well with an established radioimmunoassay technique and the sensitivity, precision and accuracy were appropriate for clinical use. Advantages of this system as compared with radioimmunoassay include the speed and simplicity of end-point detection, prolonged shelf-life of the labelled reactant and absence of any health hazard. The separation step enabled the removal of any endogenous fluorophores or other interfering factors present in biological samples.