Fluorescence quenching immunoassay of serum cortisol.

Fluorescence quenching immunoassay of serum cortisol was established. The minimal amount of cortisol detected was 3.1 ng/tube and serum concentration of 3.1 micrograms/dl to 100 micrograms/dl of cortisol could be measured. Intra- and inter-assay coefficient of variation were 7.7-10.5% and 10.7-13.3%, respectively. Cortisol values determined by the present method correlated well with those determined by radioimmunoassay (r = 0.97, y = 0.89 x + 0.88, n = 33). This fluorescence quenching immunoassay satisfied the standard criteria of dilution and accuracy, and is a rapid and simple method requiring no antibody-bound and free separation.