Which of the following indicates polyagglutination?

Polyagglutination refers to a phenomenon where red blood cells (RBCs) exhibit excessive agglutination with a variety of normal sera, leading to a situation where the RBCs appear to agglutinate with numerous different blood types. This typically occurs due to the presence of specific antigens on the erythrocyte surface that are not normally recognized by the immune system but become prominent under certain conditions, often due to changes in the molecular structure upon exposure to certain infections or antibodies.

When RBCs agglutinate with normal adult ABO compatible sera, it suggests that there are additional, unexpected agglutination reactions taking place, which is characteristic of polyagglutination. This can be a key indicator for clinicians to consider, as it often points to underlying conditions such as infections or abnormalities in the RBCs themselves.

The other options relate to different aspects of blood banking and may indicate various blood group antigens or responses but do not specifically address the unique agglutination pattern indicative of polyagglutination. For instance, weak D typing and the presence of autoantibodies may suggest different immunologic responses or blood group discrepancies but do not inherently demonstrate the broad agglutination with different sera seen in