Immunoassay definition

Similarly to the immunoassay definition, in an MIA or MIP-ILA the interaction of the target analyte with the imprinted polymer binding sites will provide a measurable result that allows quantification of the former. 

Experiments with aldicarb sulfone in ground beef involved simple extraction with acetonitrile during tissue homogenization and resulted in a definite immunoassay response at the tolerance level of 10 qg kg A moderate, but rather consistent, matrix effect was observed. A more severe matrix effect was observed in bovine milk, blood, and urine. For the liquid matrices, sample dilution was not a satisfactory strategy, because the assay variability increased at lower concentrations, negating any benefit of reducing the matrix effect. This work clearly demonsttated that matrix effects are... 

Polyclonal antibodies can react with many epitopes, whereas MAbs are restricted to one epitope on proteins that do not have repeating sequences.24 By definition, polyclonal immunoassays are generally much more sensitive but less specific than monoclonal assays. Bispecific or hybrid antibodies can be used to increase the affinity. Bispecific antibodies are formed by the fusion of two previously established hybridomas to produce antibodies displaying the binding characteristics of both of the antibodies in one molecule.25... 

High sensitivity is an intrinsically desirable property of any anal3d ical technique. The definition of sensitivity has, however, become a subject of considerable controversy particularly for immunoassays, being considered by different scientific groups as the slope in the middle of the dose-response curve [8,9], the midpoint ofthe dose-response curve (IC50) [10] or the minimal... 

In this chapter, we discuss the principles that are applied to automate the individual steps of the analytical process both in individual analyzers and in the integration of automation throughout the dinical labora.tory We provide examples of these principles as implemented in commercially available chemistry, hematology immunoassay, and nucleic acid systems point-of-care (POC) analyzers and automated specimen processing systems. Definitions of terms used in the automation of cfinical chemistry have been published by the International Union of Pure and Applied Chemistry (lUPAC). ... 

Immunoassays may not be specific for the tested drug. Similar drugs may result in a positive test for example, pseu-doephedrine, present in cold medications, may produce a positive response in immunoassays designed to detect amphetamine and methamphetamine. Therefore it is imperative that positive screening tests be confirmed by an alternate, more definitive test. The most widely accepted method for drug confirmation is GC-MS. For further discussion of this technique, the reader is referred to Chapter 7. Liquid chromatography-tandem mass spectrometry is also used for rapid detection of drugs of abuse. 

Chiral discrimination of methamphetamine isomers may be necessary to distinguish use of nonprescription nasal inhalants (R[-]-methamphetamine) from illicit use of S(-t)-methamphetamine. Some immunoassays have high specificity for S(-l-)-methamphetamine. However, definitive enantio-discrimination requires the use of a chiral derivati-zation reagent to form diastereomers of R- and S-metham-phetamine, which may be resolved using conventional GC-MS (see Figure 34-20). The Department of Defense requires chiral resolution of methamphetamine isomers. For the test to be considered positive for illicit methamphetamine use, S(-l-)-methamphetamine must be >20% of the total methamphetamine content (Table 34-8). 

Certain assay formats offer clear advantages for a particular application, however all immunoassays are based on the reversible but very specific interaction of a protein antibody with an antigen. This interaction can be described by the law of mass action. To deal with the chapters in this section, one only needs the definition of three specialized terms. First, antibodies are a group of serum proteins that react specifically with an antigen. 

Some basic immunology and definition of a few common terms will allow understanding of the central concepts of immunoassay. Antibodies are serum proteins which bind to specific molecules, called antigens, due to a complementarity of chemical structure between antibody and antigen. Immunization with an antigen preferentially induces the production of antibodies specific for... 

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