Final answer:
Tommy's blood type includes the Rh factor, indicating he is Rh positive. His exact blood type cannot be determined without ABO typing. Rhesus blood type is crucial for understanding blood compatibility, especially in transfusions and pregnancy.
Step-by-step explanation:
If a hospital lab technician has determined that Tommy has the antigen Rh on his red blood cells, Tommy's blood type would include the Rh factor. This means Tommy is Rh positive (Rh*). However, to fully determine Tommy's blood type, we need to also know about the ABO blood type—whether Tommy has A, B, AB, or O blood type molecules. Without this ABO typing, we can't specify beyond Tommy being Rh positive. Therefore, we know Tommy is either A positive, B positive, AB positive, or O positive, depending on his ABO status.
It's important to mention that the use of Rhesus blood type system is crucial because it's the second-most important blood group system after ABO. This system includes the presence of the Rh D antigen which, when present, denotes a positive Rh status, and when absent, denotes a negative Rh status.
For patients needing a blood transfusion, understanding both their ABO and Rh blood type is essential to ensure compatibility and prevent serious reactions such as hemolytic disease of the newborn, which can occur if incompatible blood is transfused or if an Rh negative mother and Rh positive fetus have an antigen-antibody reaction.