Exam 3 Chapter 11 Flashcards
Define analytical sensitivity
the ability of a test to direct very small amounts of a substance (analyte)
Define analytical specificity
the ability of a test to direct only the intended substance (analyte) without interference from similar substances
Define analyte
the substance being measured in an immunoassay, it can be an antigen or antibody
Why use labeled immunoassays
labeled immunoassays enhance sensitivity and specificity, allowing for the detection of small antigens or low concentration of antigens/antibodies
What types of labels can be used
Radioactive labels (radioimmunoassay-RIA), enzyme labels (enzyme- linked immunosorbent assay- ELISA), fluorescent labels (fluorescent immunoassays-FIA), and chemiluminescent labels
What are two types of general formats used for labeled immunoassays
Heterogenous immunoassays more sensitive of the two types, require physical separation of bound and free tractor label components by centrifugation, magnets or solid-phase binding (latex beads, micro particles, polystyrene tubes)
Homogenous immunoassays- do not require separation step
What are competitive immunoassays
all reactants are added at the same time; patient analyte and labeled reagent compete for limited binding site bound on reagent Ab; concentration of patient analyte is inversely proportional to labeled reagent
What are noncompetitive immunoassays “Sandwich” or “Capture”
patient analyte is captured by Ab bound to solid phase; then a labeled ab is added that also binds to patient analyte forming a sandwich; concentration of patient analyte is directly proportional to the labeled reagent; examples are indirect ELISA used to detect patient ag
What is the high does affect
it occurs when an excess of patient antigen leads to falsely low results because the antigen overwhelms the antibody binding sites, this can be solved by dividing the sample and retesting
What are autoantibodies
antibodies that are produced in vivo that resemble reagents antibodies, which can lead to false results in immunoassays
What are heterophile antibodies
antibodies thar react with animal proteins used in immunoassays, potentially leading to false-positive results
Define cross-reactivity
occurs when an immunoassay detects a substance other than the intended analyte, leading to false positive results
What is rapid immunochromatographic test devices
membrane-base single-use assays that use immunochromatography for rapid detection of antigens or antibodies, they involve a labeled antigen or antibody conjugated to colored latex or colloidal gold particles
When are rapid immunochromatographic tests used
for point of care testing in setting that require fast results
ex: pregnancy tests, rapid strep tests, covid-19 antigen tests, HIV rapid diagnostic tests
