enzyme-linked immunosorbent assay
Also found in: Dictionary, Thesaurus, Legal, Financial, Acronyms, Encyclopedia.
determination of the purity of a substance or the amount of any particular constituent of a mixture.
biological assay bioassay; determination of the potency of a drug or other substance by comparing the effects it has on animals with those of a reference standard.
CH50 assay a test of total complement activity as the capacity of serum to lyse a standard preparation of sheep red blood cells coated with antisheep erythrocyte antibody. The reciprocal of the dilution of serum that lyses 50 per cent of the erythrocytes is the whole complement titer in CH50 units per milliliter of serum.
enzyme-linked immunosorbent assay (ELISA) any enzyme immunoassay using an enzyme-labeled immunoreactant (antigen or antibody) and an immunoadsorbent (antigen or antibody bound to a solid support). A variety of methods are used for measuring the unknown concentration, such as either competitive binding between the labeled reactant and unlabeled unknown or a sandwich technique in which the unknown antigen binds both the immunoadsorbent and labeled antibody. One of the uses of ELISA is to screen blood for antibody to the human immunodeficiency virus; a positive result indicates probable exposure to the virus and possibly that the virus is in the blood. Since false-positives can occur, a back-up test is used to confirm positive findings.
microhemagglutination assay–Treponema pallidum (MHA-TP) a Treponema pallidum hemagglutination assay using microtechniques; used in the detection of syphilis.
radioreceptor assay a radioligand assay in which a radiolabeled hormone is used to measure the concentration of specific cellular receptors for the hormone in tissue specimens, an example being radioassay of estrogen receptors in breast tissue.
thyroid-stimulating hormone assay thyroid-stimulating hormone test.
Treponema pallidum hemagglutination assay (TPHA) a treponemal antigen serologic test for syphilis using tanned sheep red blood cells coated with antigen from the Nichol's strain of Treponema pallidum and treated patient serum; it is similar in sensitivity and specificity to the FTA-ABS test. This test is not useful for individuals who have had syphilis in the past.
TSH assay thyroid-stimulating hormone test.
en·zyme-linked im·mu·no·sor·bent as·say (ELISA),
an in vitro binding assay in which an enzyme and its substrate (rather than a radioactive substance) serve as the indicator system; in positive test results, the two yield a colored or other easily recognizable substance; tests are made in wells in polystyrene or other material to which immunoglobulins or antigenic preparations readily adsorb; the enzyme is linked to known immunoglobulin (or antigen) and in positive test results remains in the well as part of the antigen-antibody complex available to react with its substrate when added.
enzyme-linked immunosorbent assay (ELISA)
a laboratory technique for detecting specific antigens or antibodies by using enzyme-labeled immunoreactants and a solid-phase binding support, such as a test tube. A number of different enzymes can be used, including carbonic anhydrase, glucose oxidase, and alkaline phosphatase. Labeling is done by covalently binding the enzyme to the test substance through an enzyme-protein coupling agent such as glutaraldehyde. Products of the reaction may be detected by fluorometry or photometry. ELISA is nearly as sensitive as radioimmunoassay and more sensitive than complement fixation, agglutination, and other techniques.
Pros Lower cost, simpler equipment, faster ‘turn-around time’, and none of the problems inherent in handling radioactive substances
en·zyme-linked im·mu·no·sor·bent as·say(ELISA) (en'zīm-lingkt im'yū-nō-sōr'bĕnt as'ā)
A sensitive method for serodiagnosis of specific infectious diseases; an in vitro competitive binding assay in which an enzyme and its substrate rather than a radioactive substance serve as the indicator system; in positive test results, the two yield a colored or other easily recognizable substance; the enzyme is linked to known immunoglobulin (or antigen) and in positive test results remains as part of the antigen-antibody complex available to react with its substrate when added.
enzyme-linked immunosorbent assaySee ELISA TEST.
enzyme-linked immunosorbent assay (ELISA)a procedure for measuring the formation of ANTIBODY-ANTIGEN complexes adsorbed to a solid surface. An ENZYME system is linked to the complex so that after washing, the amount of enzyme activity is proportional to the amount of antigen or antibody present.
Enzyme-linked immunosorbent assay (ELISA)
A diagnostic blood test used to screen patients for AIDS or other viruses. The patient's blood is mixed with antigen attached to a plastic tube or bead surface. A sample of the patient's blood serum is added, and excess proteins are removed. A second antibody coupled to an enzyme is added, followed by a chemical that will cause a color reaction that can be measured by a special instrument.
enzyme-linked immunosorbent assay (enˑ·zīm-linkd′ imˈ·myun·ō·sorˑ·bnt aˑ·say),
n technique used to identify particular antibodies or antigens using enzyme-labeled immunoreactants. Reaction products are recorded by photometry or fluorometry. Commonly used to diagnose HIV infections.