Final answer:
Affixing antigen to a latex bead is used in an agglutination test to detect the presence of specific antibodies or antigens in a patient's serum, often indicated by the clumping of the beads.
Step-by-step explanation:
In the context of agglutination assays, antigens or antibodies can be attached to latex beads to enhance the visibility of the agglutination reaction. When these coated beads are mixed with a patient's serum, the antigens or antibodies present will cause the beads to clump together, indicating a positive agglutination and the presence of the corresponding antibodies or antigens in the serum. This method is particularly effective for detecting IgM antibodies due to their structure which provides maximum cross-linking.