In identifying antibodies, if the autocontrol is negative, what does that signify?

When the autocontrol is negative, it signals that the patient's serum does not contain autoantibodies—antibodies that would react with their own red blood cells. This finding is significant because it indicates that any antibodies present in the serum are likely directed against antigens that are not found on the patient's own red blood cells, which are referred to as alloantibodies. Alloantibodies typically arise from exposure to foreign antigens, such as those from a blood transfusion or pregnancy.

The negative autocontrol essentially rules out the possibility of an autoimmune process affecting the patient's own cells, allowing for a more focused investigation into the presence of alloantibodies that may react with donor blood during transfusions or be relevant for other transfusion-related considerations. It is crucial in blood banking and transfusion medicine to identify the nature of antibodies accurately to ensure compatibility and patient safety.