Diurnal Rhythm of Cortisol Essay Example | Topics and Well Written Essays - 1000 words

Diurnal Rhythm of Cortisol - Essay Example The most reliable way of measuring the amount of cortisol is a technique known as enzyme-linked immunosorbent assay (ELISA). There are three forms of ELISA namely competitive ELISA, sandwich and indirect ELISA. Competitive ELISA is the most dependable way of measuring salivary cortisol because it allows for the detection of active cortisol that can compete with labeled cortisol. In this assay, an antibody specific to the antigen being tested is immobilized on a well or a microtitre plate. A mixture containing a known concentration of the labeled antigen and the test sample is then added to the well. The labeled antigen and unlabeled antigen compete for the binding site on the immobilized antibody. Any unbound antigen is washed after which a substrate is added. The substrate reacts with the enzyme to form a colored substance that is then detected and the intensity of the color is measured using an ELISA reader. The intensity of the color is indirectly related to the concentration of t he antigen in the test sample. Competitive ELISA was used to determine the quantity of cortisol in the salivary samples. The wells were coated with anti-cortisol antibody at a certain concentration such that a given quantity of antigen bound to the antibodies. A mixture of a known amount of cortisol antigen labeled with peroxidase and the patient’s saliva was then added to the well. The labeled antigen competed with the unlabelled antigen to bind to the immobilized anti-cortisol antibodies in the well.