Enzyme immunoassay of 11-deoxycortisol

Enzyme immunoassay of serum 11-deoxycortisol was established by using alkaline phosphatase as a label. The labelled alkaline phosphatase was stable for at least a year. 11-Deoxycortisol in serum was purified by applying to Sephadex LH-20 column prior to present enzyme immunoassay. Separation of bound and free form was carried out by adding anti-rabbit gamma-globulin goat antiserum as a second antibody. The minimal amount of 11-deoxycortisol detected was 40 pg/tube and the measurable range was from 0.04 to 10 micrograms/dl. Intra- and interassay coefficient of variations were 3.8-4.5% and 3.4-5.3%, respectively. 11-Deoxycortisol values determined by the present method correlated well with those determined by radioimmunoassay (r = 0.98, y = 0.93 x + 0.19, n = 28). This enzyme immunoassay satisfied the standard criteria of dilution and accuracy, and is applicable to routine determination of serum 11-deoxycortisol in any clinical laboratory as a non-isotopic immunoassay.