Define the following terms, and give an example of how each reaction is used diagnostically:
a. viral hemagglutination
b. hemagglutination inhibition
c. passive agglutination

Verified step by step guidance

1. Define 'viral hemagglutination': This is a process where viruses cause red blood cells to clump together. It is used diagnostically to identify the presence of certain viruses, such as the influenza virus, by observing the clumping of red blood cells in the presence of the virus.
2. Provide an example of viral hemagglutination: In the laboratory, a sample suspected of containing the influenza virus is mixed with red blood cells. If hemagglutination occurs, it indicates the presence of the virus.
3. Define 'hemagglutination inhibition': This is a reaction where antibodies prevent viruses from causing hemagglutination. It is used diagnostically to determine the presence of specific antibodies against a virus in a patient's serum.
4. Provide an example of hemagglutination inhibition: In a diagnostic test, a patient's serum is mixed with a known virus and red blood cells. If hemagglutination is inhibited, it suggests the presence of antibodies against the virus in the serum.
5. Define 'passive agglutination': This is a reaction where particles, such as latex beads, are coated with antigens or antibodies and agglutinate in the presence of the corresponding antibody or antigen. It is used diagnostically to detect the presence of specific antigens or antibodies in a sample.

Key Concepts

Viral Hemagglutination

Viral hemagglutination is a process where certain viruses can agglutinate red blood cells (RBCs) by binding to sialic acid residues on their surface. This reaction is used diagnostically to identify the presence of specific viruses in a sample, as the agglutination indicates viral activity. For example, the hemagglutination test can be employed to detect influenza viruses in respiratory samples.

Hemagglutination Inhibition

Hemagglutination inhibition is a diagnostic technique that measures the ability of antibodies to prevent the agglutination of RBCs by viruses. If antibodies are present in a sample, they will bind to the virus and inhibit its ability to agglutinate RBCs. This method is commonly used to determine immunity to viruses, such as in the case of rubella or measles, by assessing the presence of specific antibodies in a patient's serum.

Passive Agglutination

Passive agglutination involves the coating of inert particles, such as latex beads, with antigens or antibodies to facilitate the detection of specific antibodies or antigens in a sample. This method enhances the visibility of agglutination reactions, making it easier to diagnose infections. For instance, passive agglutination tests can be used to detect streptococcal infections by identifying antibodies against streptococcal antigens in a patient's serum.