SYNOPSIS INTRODUCTION PRINCIPLE HISTORY HOW TO RIA WORK METHOD APPLICATION OF RIA ADVANTAGE DISADVANTAGE CONCLUSION REFERENCES The technique in which a radioisotope is used as a tag or label (i.e. radioisotope covalently linked to antigen or antibody) for the detection of antigen-antibody complex is known as RIA. RIA involves the separation of a protein (from a mixture) using the specificity of antibody - antigen binding and quantifitation using radioactivity. RIAs utilize a radioactive label (usually 125I, 3H or 14C), which emits radiation that can be measured with a beta or gamma counter.