What indicates a positive Rh blood type?

A positive Rh blood type is indicated by the presence of the D antigen, which is part of the Rh blood group system. The D antigen is a specific type of protein found on the surface of red blood cells, and when this antigen is present, it designates the blood type as Rh positive.

In the context of blood typing, the Rh factor is crucial for compatibility in blood transfusions and pregnancy. Individuals who have the D antigen are regarded as Rh positive, while those who lack it are Rh negative. This distinction plays a significant role in understanding immune responses and transfusion reactions, as the presence or absence of the D antigen can lead to the formation of antibodies if incompatible blood is introduced into the body.

The other choices relate to different blood types and antigens:

• The presence of A antigen indicates blood type A, but does not speak to the Rh factor.

• The presence of both A and B antigens indicates blood type AB, again not addressing the Rh status.

• The absence of H antigen does not have relevance in the context of the Rh factor, as H antigen is primarily associated with the ABO blood group system, not the Rh system.

Thus, the presence of the D antigen is the correct indicator of a positive Rh