Radioimmunoassay of Urinary Free Cortisol.
NAVAL HEALTH RESEARCH CENTER SAN DIEGO CALIF
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The radioimmunoassay for urinary free cortisol described in this paper is simple, rapid, and reproducible. The method uses a commercially available antibody preparation and is performed in two steps. The first step includes an extraction and a column purification to remove materials antigenically similar to cortisol from the urine. The second step is the radioimmunoassay using dextran coated charcoal to separate bound and unbound cortisol. H3-cortisol is added prior to any mechanical manipulation to allow calculation of analytical recovery for the purification procedure. The coefficient of variation for interassay determinations was a maximum of 10.3 and for intra-assay determinations a maximum of 5.7. Analytical recovery averaged 97.7. One technician can analyze 100 samples per week. Author