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 an enzyme coupled to a second antibody. The presence of a substance can be measured accurately as a result of colour changes that occur following reaction between the enzyme and its substrate 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.