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.