Assay

An assay is an analysis done to determine: {{}}The presence of a substance and the amount of that substance. Thus, an assay may be done for example to determine the level of thyroid hormones in the blood of a person suspected of being hypothyroid (or hyperthyroid). The biological or pharmacological potency of a drug. For example, an assay may be done of a vaccine to determine its potency. Assay is also used as a verb and has several related meanings in this role: To try or attempt. For example, "she assayed this operation for the first time and so was understandably nervous." To analyze a mixture for one or more of its components To judge the value, the worth of something. The words "assay" and "essay" are often confounded, a cardinal sin according to some word mavens. However, "assay" and "essay" share a common ancestry. Both words come from the French "essai" which in turn came from the Late Latin "exagium" meaning the "act of weighing".

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1. The quantitative or qualitative evaluation of a substance for impurities, toxicity, etc; the results of such an evaluation. 2. To examine; to subject to analysis. 3. Test of purity; trial. [M.E., fr. O.Fr. essaier, fr. L.L. exagium, a weighing]

- Ames a. SYN: Ames test.

- biologic a. SYN: biotest.

- clonogenic a. in vitro culturing of neoplastic cells to test their radiosensitivity or chemosensitivity, and probable clinical efficacy of a therapeutic agent.

- competitive binding a. general term for an a. in which a substance competes for labeled versus unlabeled ligand; following separation of free and bound ligand, the concentration of unlabeled ligand is inversely proportional to the amount of labeled bound ligand. Values are compared to known standards. SEE ALSO: enzyme-linked immunosorbent a., radioreceptor a., immunoassay, enzyme-multiplied immunoassay technique, radioimmunoassay. SYN: displacement analysis, saturation analysis.

- complement binding a. SYN: complement fixation.

- double antibody sandwich a. for antigen; an application of the ELISA method in which material being tested for antigen is added to wells coated with known antibody; the presence of antigen fixed to the antibody coat can be determined either directly, by adding antibody linked to the enzyme of the indicator system, or indirectly, by first adding unlabeled known antibody, the attachment of which to the antigen can be demonstrated by addition of immunoglobulin-specific antibody linked to the enzyme.

- EAC rosette a. (ro-zet′ as′sa) EAC rosette.

- enzyme-linked immunosorbent a. (ELISA) an in vitro binding a. in which an enzyme and its substrate (rather than a radioactive substance) serve as the indicator system; in positive tests, 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 tests remains in the well as part of the antigen-antibody complex available to react with its substrate when added.

- Grunstein-Hogness a. a procedure for identifying plasmid clones by colony hybridization.

- hemizona a. (hem′e-zo-na) diagnostic test evaluating the binding capacity of sperm to the zona pellucida.

- hemolytic plaque a. SYN: Jerne plaque a..

- immunochemical a. SYN: immunoassay.

- immunoradiometric a. an a. that differs from conventional radioimmunoassay in that the compound to be measured combines directly with radioactively labeled antibodies.

- indirect a. for antibody; an application of the ELISA method in which serum being tested for antibody is added to wells coated with known antigen; presence of antibody bound to the antigen coat can be determined by addition of immunoglobulin-specific antibody to which is linked the enzyme of the indicator system, followed by addition of substrate to the washed aggregate.

- Jerne plaque a. an a. that enumerates individual antibody-forming cells. SYN: hemolytic plaque a..

- Lowry-Folin a. SYN: Lowry protein a..

- Lowry protein a. a method for determining protein concentrations using the Folin-Ciocalteu reagent. SYN: Lowry-Folin a..

- radioreceptor a. a competitive binding a. in which the binder is a membrane or tissue receptor rather than an antibody.

- Raji cell radioimmune a. for immune complexes; a procedure by which immune complexes adsorbed from a test serum by a standard preparation of lymphoblastoid (Raji) cells are assayed by the capacity to bind ¹²⁵I-labeled antibody to immunoglobulin.

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as·say 'as-.ā, a-'sā n

1) examination and determination as to characteristics (as weight, measure, or quality)

2) analysis (as of a drug) to determine the presence, absence, or quantity of one or more components compare BIOASSAY

3) a substance to be assayed also the tabulated result of assaying

as·say a-'sā, 'as-.ā vt to analyze (an impure substance or mixture) for one or more specific components <the sample was \assayed for drug content>

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n.

a test or trial to determine the strength of a solution, the proportion of a compound in a mixture, the potency of a drug, or the purity of a preparation. See also bioassay.

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as·say (asґa) determination of the amount of a particular constituent of a mixture, or determination of the biological or pharmacological potency of a drug.