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assay

 [as´a]
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.
 ELISA: With antigen capture ELISA, the wells are coated with antibody to the virus. The sample containing virus (1) is added and, after washing several times, enzyme conjugated to an antibody to the virus is added (2). Finally, after a further cycle of washing, the enzyme's substrate (3) is added. A colored product is formed if the viral antigen is present in the sample (4). From Hart and Shears, 1997.
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.

as·say

(as'sā, ă-sā'),
1. The quantitative or qualitative evaluation of a substance for impurities, toxicity, or other characteristics; 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]

assay

A quantitative or qualitative procedure for detecting the presence, estimating the concentration, and/or determining the biological activity* of a macromolecule (e.g., an antibody or antigen, molecule, ion, cell, pathogen, etc.). Assays are based on measurable parameters that allow differentiation between sample and control. Biological assays (not to be confused with animal testing for drug efficacy and safety) are of historic interest, as they are cumbersome, difficult to quantify and rarely provide information that is not obtainable by other testing formats.

assay

Lab medicine The quantification of a substance of interest by a specific chemical, enzymatic, immunologic or radioimmune-mediated reaction

as·say

(as'ā)
1. To examine or analyze.
2. A test of the biologic potency of something (e.g., medicine).
[M.E., fr. O.Fr. essaier, fr. L.L. exagium, a weighing]

assay

Qualitative or quantitative analysis of a substance such as a drug.

Assay

An analysis of the chemical composition or strength of a substance.

as·say

(as'ā)
1. The quantitative or qualitative evaluation of a substance for impurities, toxicity, or other characteristics; 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]
References in periodicals archive ?
One of his best-known statements comes from The Assayer: "Philosophy is written in this grand book, the universe, which stands continually open to our gaze.
In addition he found fragments of chemical glassware, assayers' flasks and retorts for distilling liquids.(29) It is possible that this testing equipment was used by Hariot, the English naturalist.
Occasional assayers' marks were removed from small or damaged plate to be soldered onto a larger piece.
Theodore Lowe talked a Denver assayer into analyzing it, and it turned out to be gold ore worth $200 per ton (nearly 10 troy ounces of gold per ton--good enough to cause a stampede in most places!).
"Most homes had a blowtorch, and every hobbyist, machine shop, farmer, logger, dentist, assayer and everyone in the trades--painters, plumbers, tinsmiths, mechanics--all utilized them."
Near the end of the Discourse Descartes alludes to, without mentioning, the name of Galileo, whose essay The Assayer (Il Saggiatore) had been a major influence on the Mersenne Circle.
After his resignation from Bordeaux in 1848, Laurent became Assayer at the Paris Mint where he built a private laboratory.
Major Works: The Sidereal Messenger (1610), The Assayer (1623), Dialogue on the Two Great World Systems (1632), Discourses on Two New Sciences (1638)
When Ezra was three, his father, Homer, obtained an assayer's job at the U.S.
Anchorage, AK 99503 assayer, refiner and bullion dealer
During the second half of the 18th century, mining, and above all the prospecting for new orebodies, were performed more rationally under the direction of leading Swedish experts such as the famous mineralogist, chemist and assayer Axel Fredrik Cronstedt (1722-1765).