<P> RBCs are used to restore oxygen - carrying capacity in people with anemia due to trauma or other medical problems, and are by far the most common blood component used in transfusion medicine . Historically they were transfused as part of whole blood, are now typically used separately as RBCs and plasma components . The process of identifying a compatible blood product for transfusion is complicated . </P> <P> Side effects can include allergic reactions including anaphylaxis, red blood cell breakdown, infection, and lung injury . Giving incompatible RBCs to a person can be fatal . </P> <P> To avoid transfusion reactions, the donor and recipient blood are tested, typically ordered as a "type and screen" for the recipient . The "type" in this case is the ABO and Rh type, specifically the phenotype, and the "screen" refers to testing for atypical antibodies that might cause transfusion problems . The typing and screening are also performed on donor blood . The blood groups represent antigens on the surface of the red blood cells which might react with antibodies in the recipient . </P> <P> The ABO blood group system has four basic phenotypes: O, A, B, and AB . In the former Soviet Union these were called I, II, III, and IV, respectively . There are two important antigens in the system: A and B. Red cells without A or B are called type O, and red cells with both are called AB . Except in unusual cases like infants or seriously immunocompromised individuals, all people will have antibodies to any ABO blood type that isn't present on their own red blood cells, and will have an immediate hemolytic reaction to a unit that is not compatible with their ABO type . In addition to the A and B antigens, there are rare variations which can further complicate transfusions, such as the Bombay phenotype . </P>

In what type of clinical situation would you receive just blood platelets during a blood transfusion