Immunoassay immunoradiometric

M15. Marz, W., Siekmeier, R., Gross, E., and Gross, W., Determination of lipoprotein(a) Enzyme immunoassay and immunoradiometric assay compared. Clin. Chim. Acta 214, 153-163 (1993). 

Clearly, all of the related substances, with the exception of hGH dimer, exhibited full biopotency as compared to hGH monomer. Further investigation of hGH dimer demonstrated that traditional immunoassays could not distinguish it from hGH monomer, although an immunoradiometric (IRMA) assay using two monoclonal antibodies could distinguish the two forms (8). As expected, size exclusion HPLC was also able to distinguish monomeric and dimeric forms of hGH. Further studies revealed that the IRMA assay precision was approximately 5-6% RSD, whereas size exclusion HPLC exhibited a precision of 1-2% RSD. Therefore, size exclusion HPLC was selected as the most useful candidate for replacement for the in-vivo bioassay. 

Competitive binding immunoassay (e.g., RIA) Enzyme-linked immunosorbent assay (ELISA) Immunoradiometric assay (IRMA) — dual monoclonal antibody assay Receptor binding assay Cell binding assay... 

Several methods have been described, starting with radio-immunoassay procedures (Rees 1971, Kao 1979, Krieger 1975), and proceeding to immunoradiometric methods (Hodgkinson 1984, White 1987, Zahradnik 1989, Raff 1989, Gibson 1989, Fukata 1989). 

The theory and procedure for several immunoradiometric assays are given in the chapters by Hales and Woodhead and by the Merretts." I-labeled protein A is rapidly becoming a valuable tracer in immunoassays. It can bind to the F,. region of IgG molecules without inhibiting the reaction between antigen and antibody. Procedures in which an antibody or protein A are iodinated are particularly useful when the antigen cannot be labeled. 

Currently, immunoassay is the practical method of choice for measuring cytokines and their receptors. As cytolanes are proteins, specific antibodies can be raised against recombinant cytokines and have also been measured as an indicator of cytokine presence, The general characteristics of cytokine immunoassays are comparable with the classical immunoassays, with monoclonal, oligoclonal, or polyclonal antibodies all being used (see Chapter 9). The most popular formats are immunoradiometric assay (IRMA) and ELISA, which use a first monoclonal antibody for the capture and a second antibody labeled with a radioisotope or an enzyme. 

The original inhibition test has been replaced by an immunoradiometric assay and a time-resolved fluorescent immunoassay (the DELFIA method developed by Pharmacia, Uppsala, Sweden). The cut-off values for healthy subjects vary from 14 to 20 kU/L, depending on the method. 

Serum ferritin assay may be performed by any of several methods, including immunoradiometric assay, ELISA, and immunochemiluminescent and immunofluoro-metric methods. Reagents for this assay are available in kit form and in automated immunoassay instruments from several manufacturers. The manufacturers instructions should be followed. 

Signal antibodies have most often been radiolabeled (for immunoradiometric assays [IRMA]) with ( 25j) 7,62,i%,344,4i4 labeled with a chemiluminescent (for immunochemilummo-metric assays [ICMA]) compound, such as acridinium ester, or an enzyme (enzyme-linked immunosorbent assay [ELISA] or enzyme immunoassay [EIA]), such as ALP, converting a substrate (1,2-dioxetane phosphate) to a chemiluminescent product. 

Preissner C, Klee G, Krco C. Nonisotopic sandwich immunoassay of thyroglobulin in serum by the biotin-streptavidin technique Evaluation and comparison with an immunoradiometric assay. Clin Chem 1988 34 1794-8. 

TM Jackson, NJ Marshall, RP Ekins. Optimization of immunoradiometric assays. In WM Hunter, JET Corrie, eds. Immunoassays for Clinical Chemistry. Edinburgh Churchill Livingstone, 1983, p 557. 

For each type of assay, the label or tag involved is listed along with typical substrates, type of absorbance, and type of instrument required. RIA radioimmunoassay IRMA immunoradiometric assay CPM counts per minute ELISA enzyme linked immunosorbent assay EIA enzyme immunoassay TMB 5,5 tetramethylbenzidine HPA p hydroxyphenylacetic acid AMPPD 4 methoxy 4 (3 phosphatephenyl) spiro(l,2 dioxetane) 3,2 adamantane p NPP p nitrophenyl phosphate 4 MUP 4 methylumbelliferyl phosphate ONPG o nitrophenyl P galactopyranoside MUG 4 methylumbelliferyl P D galactopyrano side AMPGD 3 (4 methoxyspiro( 1,2 dioxetane 3,2 tricyclo(3.3.1.1(3,7))decan) 4 yl)phenylgalacto pyranoside ECL electrochemiluminescence. 

Methods based on radiolabels continue to hold an important place in routine analysis and in research related to clinical testing. The main techniques included in this group are radioimmunoassy (RIA), immunoradiometric assay (IRMA), and scintillation proximity assay (SPA). Many researchers in this field use short-lived radioisotopes and chelating agents in antibody labeling.139 The most popular types of immunoassay are methods that use enzymatic labels the enzyme-linked immunosorbent assay (ELISA), the enzyme-monitored immunotest (EMIT), the competitive binding enzyme immunoassay (EIA), and the immunoenzymometric assay (IEMA). 

The response of a surface antigen-antibody reaction can also be mediated by an electron transfer reagent. This has been demonstrated by Robinson et al. in their studies on electrochemical immunoassays for hCG and thyroxine. In the analysis of hCG, a two-site amperometric immunoassay was developed in which monoclonal capture antibodies were immobilised on the surface of a glassy carbon electrode. A second antibody against hCG was labelled with glucose oxidase. The electrode was used both to separate free from bound enzyme-antibody conjugate and to assay the enzyme activity electrochemically by use of dimethylaminomethyl ferrocene as an electron transfer mediator. This method was found to correlate well with an immunoradiometric assay. In the analysis of thyroxine, another ferrocene derivative, namely ferrocenemonocarboxylic acid, was used as the electron transfer mediator. ... 

An alternative approach to immunoassay was described by Miles and Hales (2) and termed immunoradiometric assay (IRMA), since it initially used isotopically labelled antibodies. In this type of assay the labelled component is a specific antibody (Ab ), the process again being based on the antigen-antibody binding reaction ... 

The new particles also seem to have significant advantages in different immunoassays. Immunoassays can be divided into 3 groups dependent upon the detection method, namely particle counting immunoassays (PACIA) radioimmunoassays (RIA) and immunoradiometric assays (IRMA) and enzymlinked immunoassays (ELISA). ... 

Techniques for the detection or assay of various substances based on the reaction of those substances with specific antibodies (or vice versa, i.e. the detection and assay of antibodies using antigens). Such techniques include agglutination reactions, automated immune precipitation, complement fixation tests, crossed electrophoresis, counter electrophoresis, double diffusion, enzyme immunoassay, fluoroimmunoassay, haem-agglutination, immunoelectrophoresis, immunofluoresence, radial immunodiffusion, spin immunoassay, immunofixation, immunoradiometric assay and radioimmunoassay. See separate entries for these subjects. 

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