Immunoradiometric assay

Immunoradiometric assay (IRMA) is an assay that uses radiolabeled antibodies. It differs from conventional radioimmunoassay (RIA) in that the compound to be measured combines immediately with the radiolabeled antibodies, rather than displacing another antigen by degrees over some period.

Introduction

Fluorescent and radioactive antibodies have been used to locate or measure solid-phase antigens for many years. However, only recently has the labeled antibody been applied to measurement of antigen to sample. The method converts the unknown antigen into a tracable radioactive product. Immuno radiometric assay (IRMA) was first introduced by "Miles and Hales" in 1968.

Principle

In IRMA, the antibodies are labeled with radioisotopes which are used to bind antigens present in the specimen. When a positive sample is added to the tubes, radioactively labeled (labeled with I125 or I131 radioisotopes) antibodies bind to the free epitopes of antigens and form an antigen-antibody complex. Unbound labeled antibodies are removed by a second reaction with a solid phase antigen. The amount of radioactive remaining in the solution is direct function of the antigen concentration.

Medical tests: Immunologic techniques and tests (CPT 86000–86849)

Immunologic techniques
and tests

serology/
diagnostic immunology

Immunoprecipitation	Chromatin immunoprecipitation Immunodiffusion Ouchterlony double immunodiffusion Radial immunodiffusion Immunoelectrophoresis Counterimmunoelectrophoresis

Immunoassay	ELISA ELISPOT Enzyme Multiplied Immunoassay Technique RAST test Radioimmunoassay Radiobinding assay Immunofluorescence

Agglutination	Hemagglutination/Hemagglutinin Coombs test Latex fixation test

Other	Nephelometry Complement fixation test Immunocytochemistry Immunohistochemistry Direct fluorescent antibody Epitope mapping Skin allergy test Patch test

Inflammation

CBC
- lymphocyte count

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