Immunoassay Analyzers And Assays
August 11, 2021
INTRODUCTION Immunoassay analysers are applied to a situation where one wants to detect or isolate a molecule within a mixture, usually using an antibody as a reagent. (Beckmancoulter, 2021) These devices perform a variety of tests including those targeting cancer, allergies, therapeutic drug monitoring and more. And they typically include an autosampler, a reagent dispenser, a washer, and a detection system. (Who.int, 2021) Modern immunoassay analysers often come with advanced, user-friendly features such as touchscreen interface, easy-to-use software and ready-to-use reagents. With advanced analysers, laboratories can benefit from simple and trouble-free operation, workflow flexibility, fast turnaround times, and broad measuring ranges. (Block Scientific Inc, 2021) TYPES AND VARIATIONS Five types of immunoassay, enzyme immunoassay (EIA), radioimmunoassay (RIA), fluoroimmunoassay (FIA), chemiluminescent immunoassay (CLIA) and counting immunoassay (CIA), are generally used. Depending on configuration and levels of sophistication, as well as available testing options, different immunoassay analysers could vary greatly. (Martínez, 2021) Radioimmunoassay The radioimmunoassay is perhaps the oldest types of immunoassays. Here, a radioisotope is attached to an antigen of interest and bound with its complementary antibody. Then a sample with the antigen to be measured is added. It competes with the radioactive antigen, kicks it out of the binding spot and replaces it. After washing away unbound antigens the radioactivity of the sample is measured. The amount of radioactive signal is inversely related to the amount of target antigen. The health hazards of using radioactive substances caused a movement toward safer methods. (Martínez, 2021) Counting immunoassay In a counting immunoassay, polystyrene beads are coated with many antibodies complementary to the target antigen. During incubation the beads bind to multiple antigens and group together into a large mass. Some beads remain unbound. The entire solution is passed through a cell counter and only the unbound beads are counted. The number of unbound beads is inversely proportional to the amount of antigen. (Martínez, 2021) Enzyme-linked immunosorbent assay The Enzyme-Linked Immune Sorbent Assay, also known as ELISA, determines various entities such as the presence of antibodies to an infectious disease and also detects and measures antibodies in human samples as a reaction to specific antigens. ELISA-tests are commonly used to test the concentration of Vitamin D, insulin, COVID-19 or hepatitis antigens in samples. (Future Diagnostics, 2021) Fluorescence and Chemiluminescence Immunoassays Besides the use of immunoassays based on colour intensity to detect antibodies in specimens, detection can also be done by fluorescent tracers and light-generating molecules. These are called Fluorescent Immunoassay (FIA) and Chemiluminescence Immunoassay (CLIA). The basis of these immunoassays is a variant of ELISA. T...
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