enzyme-linked immunosorbant assay

In medicine, technique for accurately determining the quantity of a substance in a sample, for example hormone levels in a blood sample. It involves the preparation of an antibody to the substance and the enzyme to which the antibody binds. The presence of a substance can be measured accurately as a result of colour changes that occur following reaction between the antibody and the enzyme in the presence of the substance. The ELISA technique is used in the detection of altered hormone levels in the urine in pregnancy testing kits.