Enzyme immunoassay for cortisol in serum using cortisol 21-amine

Cortisol 21-amine (21-amino-11beta,17-dihydroxy-4-pregnene-3,20-dione) was prepared and an enzyme immunoassay for cortisol in serum was established using cortisol 21-amine conjugated with alkaline phosphatase. The minimal amount of cortisol detected was 1ng/tube and the measurable range was from 1 to 80 microgram/d1, using 10 mu 1 of serum sample. This enzyme immunoassay satisfied the standard criteria of dilution, accuracy and precision. The values correlated well with those obtained by radioimmunoassay. This enzyme immunoassay is applicable to the routine determination of serum cortisol in any clinical laboratory. Cortisol 21-amine was found to be a useful derivative for preparing cortisol-enzyme conjugate in enzyme immunoassay.