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| Definition of Immunoassay |
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Definition
| test that used antibody and antigen complexes as a means of generating a measurable result |
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| an immune response that causes the body to generate antibodies |
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| a test that can be performed |
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| a protein that is produced by the body in response to an invading substance |
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| substance that the body is trying to fight off |
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| anything measured by a laboratory test |
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| each site on an antigen that can bind antibodies |
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| Function of an Antibody in Assays |
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Definition
| antibodies posses high specificity and affinity for a specific antigen, the specific binding of an antibody to an antigen allows the detection of analytes |
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Definition
| type of protein called immunoglobulins, the most common is IgG |
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| Antibody Structure - Fab Region |
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Definition
| contains the antigen binding site, the "arms" of the Y |
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| Antibody Structure - Fc region |
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Definition
| region of constant structure with an antibody class, the "leg" of the Y |
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Definition
only bind to one antigen epitope
reduces the occurrence of false positives |
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| less specific to antigen epitopes and have varying binding affinities, therefore more likely to produce a false positive |
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| Polyclonal Antibody Production |
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Definition
animal is injected with antigen which generates an antibody response
antibodies are collected as blood contains a hetergogenous mixture of varying affinities and specificities |
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Definition
the likelihood of separation after an antigen/antibody complex is formed
stronger the avidity and affinity, the greater possibility of cross reactivity |
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| a low molecular weight antigen that has one epitope |
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binding of an antigen and antibody
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| a molecule that reacts as part of the assay, and in doing so produces a signal that can be measured |
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Definition
| nucleus emits charged electrons or positively charged particles (positrons) |
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| emitted electrons from a beta emission |
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| radio nuclide most commonly used in beta emission |
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Definition
electromagnetic radiation (short wavelength) from an unstable nuclei
energy released emits a fluor which produces a photon of light with is amplified and measured by a photomultiplier tube |
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Definition
biologic catalysts (increase rate of reaction but are not consumed)
measured by photometric, fluorometric, or chemilum methods |
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Definition
fluorochromes or flurophors
absorb radiant energy of one wavelength and emit energy at a longer wavelength in less than 4 - 10 seconds
detected using a fluorometer |
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Definition
emit a photon of light as the result of a chem or biochemical reaction
luminol commonly used |
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Term
| Ligand Assays that use a Label |
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Definition
isotopic RIA
EIA
FIA/FPIA
luminescence
chemiluminescence
bioluminescence |
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Definition
radio immuno assay
detected by liquid scintiallation counter, gamma counter |
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enzyme immuno assay
detected by photometer, fluorometer, luminometer |
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fluoroescent immuno assays
detected by fluorometer |
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| Immunoassays that don't use a Label |
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Definition
direct (RID)
nephelometry
turbidometry
reflectance |
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Term
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Definition
unlabeled analyte in the test sample is measured by its ability to compete with labeled antigen in the immunoassay
less signal means more patient antigen/more signal means less patient antigen |
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| One Step Competitive Format |
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Definition
| both the labeled antigen reagent and the unlabeled specimen compete for a limited amount of antibody |
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| Two Step Competitive Format |
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Definition
antibody added in excess, then antigen added, binding occurs, unbound antibody is washed away
add additional unbound antibody, labeled antigen added to bind to whatever unbound antibody is left over |
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| Noncompetitive (Sandwich) Method |
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Definition
analytes are bound between two highly specific antibody reagents
measured labeled analyte is directly proportional to the amount of antigen present (more antigen that is present more labeled antibody will bind) |
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Definition
requires separation of bound antibody/antigen complex
can take longer to perform |
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does not require separation of the bound antibody/antigen
much easier and faster to perform
usually measure small analytes like drugs |
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| enzyme linked immunoabsorbant assay |
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