How do autoantibodies typically affect compatibility testing results?

Autoantibodies can have a significant impact on compatibility testing results and are known to cause abnormalities in various tests performed before blood transfusions. Specifically, in the context of compatibility testing, autoantibodies can interfere with several key components such as the ABO and Rh typing, antibody screening, and crossmatching.

When autoantibodies are present, they may react with the patient's own red blood cells or with the red blood cells from donor units during testing. This reaction can lead to unexpected results, causing difficulties in accurately determining blood group antigens or in identifying compatible blood for transfusion. For instance, in antibody screenings, autoantibodies can cause false positives, making it seem like there are clinically significant antibodies present even when none exist. Similarly, during the crossmatch process, the presence of autoantibodies can lead to discrepancies, complicating the selection of compatible blood products.

This multiplicity of potential issues stemming from autoantibodies underscores why the correct answer emphasizes that the key compatibility tests—ABO, Rh, antibody screen, and crossmatch—may show abnormal results when autoantibodies are present. The overall impact of these autoantibodies on compatibility testing is both significant and complex, often requiring additional investigation and careful