Improvement of antisera for cortisol immunoassay by reduction of endogenous hormone concentrations

Markedly elevated concentrations of endogenous steroids in antisera may reduce the potential sensitivity of immunoassays. Attempts to raise antisera containing reduced amounts of cortisol by adrenalectomy, or concomitant administration of synthetic corticosteroid during immunisation, have met with indifferent success. Removal of cortisol, using dextran-coated charcoal in buffer of optimum molarity, may increase the average affinity constant of the antiserum, and improve the assay sensitivity and specificity.