What is considered a universal donor in low titer group O whole blood?

The designation of a universal donor in the context of low titer group O whole blood is based predominantly on the presence of antigens on red blood cells. In blood transfusions, compatibility is vital to avoid hemolytic reactions, which can occur when the recipient's immune system recognizes foreign antigens.

Group O blood is considered a universal donor type for red blood cell transfusions because it lacks A and B antigens on the surface of the red blood cells. Consequently, individuals with blood type O can donate to any other blood type without the risk of the recipient's immune system attacking the transfused red blood cells.

When assessing the Rh factor in conjunction with blood type, O negative is particularly significant because it not only lacks A and B antigens but also lacks the Rh factor (D antigen). This makes O negative blood the safest choice during emergencies or situations where the blood type of the recipient is unknown, as it can be safely given to anyone.

In contrast, O positive blood can still carry the Rh factor which, while compatible with Rh-positive individuals, does not possess the same universal donor quality as O negative blood when considering a broader context that includes Rh compatibility. The other blood types indicated in the choices, like A negative and B negative,