8. Immunodiagnostics

What are immunodiagnostics?

Diagnostic tests that use antibodies to detect antigens or antibodies in a sample

What are the two main types of immunodiagnostic tests?

Tests that detect antibodies in a sample and tests that detect antigens using antibodies

What is an antigen?

A substance that triggers an immune response, usually proteins or sugars found on the outside of cells

What is an antibody?

A protein produced by the immune system in response to an antigen

What is the key principle of immunoassays?

The specific binding between antibodies and antigens

What are two main factors immunodiagnostic tests can detect for infectious diseases?

Presence of infection (pathogen/antigen) and evidence of exposure (antibodies)

What are molecular targets used in immunodiagnostics?

Antigens, antibodies, and specific proteins or other molecules

What is precipitation in immunodiagnostics?

A reaction where antibodies and antigens interact to form an insoluble product

What is agglutination in immunodiagnostics?

The process of antibodies binding to antigens and clumping them together

What is AGID?

Agar Gel Immunodiffusion, a test where antigen and antibody migrate towards each other through agar gel

What is ELISA?

Enzyme-Linked Immunosorbent Assay, a plate-based assay technique for detecting and quantifying substances

What are the four main types of ELISA?

Direct, indirect, sandwich, and competitive

What is a lateral flow immunoassay?

A paper-based device for detecting and quantifying analytes in complex mixtures

What is immunofluorescence?

A technique using fluorescent-labeled antibodies to visualize specific antigens

What is immunohistochemistry?

A method for detecting specific antigens in tissue sections using antibodies

What is a radioimmunoassay?

A technique that uses radioactively labeled antigens to quantify specific antigens in patient serum

What are exogenous antigens?

External antigens that enter the body from outside, such as viruses and pollen.

What are endogenous antigens?

Antigens that exist on cells inside the body, including xenogenic, allogenic, and autologous antigens.

What is the role of immunoglobulins?

They are antibodies designed to bind specifically to antigens and neutralize them.

How do immunodiagnostics detect the presence of infection?

By looking for pathogens or antigens in a sample.

What is the difference between qualitative and quantitative ELISA?

Qualitative ELISA provides a Yes/No answer, while quantitative ELISA measures the concentration of antibodies or antigens.

What is a lateral flow immunoassay?

A test that uses a liquid sample applied to a pad that travels laterally through a conjugate pad and onto a test membrane.

What is the purpose of using a conjugate pad in lateral flow assays?

It contains labeled reagents and antibodies that react with the sample as it flows through.

What is immunofluorescence used for?

To visualize antigen-antibody complexes by detecting fluorescently labeled antibodies bound to specific antigens.

What is immunohistochemistry (IHC)?

A method used to detect specific antigens in tissue sections using antibodies for diagnostic purposes.

What is radioimmunoassay (RIA)?

A technique that quantifies specific antigens in serum using radioactively labeled antigens, though it is rarely used today.

What factors should be considered when selecting an immunoassay?

Accuracy, repeatability, reliability, quality control, cost, testing time, and patient welfare.