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CLS 1113 Introduction to Clinical Laboratory Practices Unit 5 Labeled Immunoassays Chapter 10 Labeled Immunoassays • Designed for Ags and Abs that DO NOT react in precipitation or agglutination tests due to their small size or low concentrations. • Indirect method of detection: • Competitive vs. Non-Competitive – Test Antigen or Antibody competes for binding sites Elements of Labeled Immunoassays • Ligands • Antibodies • Standards or Calibrators • Separation Methods • Detection of Label Radioimmunoassay (RIA) • Competitive binding assay • Uses a radioactive substance as a label – 3H - Tritiated hydrogen – 125I - Iodine 125 Radioimmunoassay • Two Types – Number 1 Radioimmunoassay Number 2 Enzyme Immunoassay • Immunoassay labels • Enzymes – – – – Cheap Readily available Long shelf life Easily adapted to automation ELISA, Figure 10-4, page 149 Enzyme Immunoassay • Enzymes are naturally occurring molecules that catalyze specific biochemical reactions. • They react with suitable substances to produce products that are chromogenic (color), fluorogenic, or luminescent. ELISA: Sandwich method Figure 10-5, page 149 Fluorescent Immunoassay • Similar to ELISA but a fluorochrome is used rather than an enzyme. • Fluorochromes have the ability to absorb energy from light an emit it at a longer wavelength. Fluorescent Immunoassay: Direct and Indirect Chemiluminescent Immunoassays • Chemiluminescence is the production of light energy due to a chemical reaction. • Certain substances when oxidized can give off short or long bursts of light energy.
