Prevention - Red Cell Alloimmunization

Alloimmunization cannot be entirely prevented except by transfusions from an identical twin or by autologous transfusions. Leukoreduction of cellular components reduces the incidence of alloimmunization to leukocyte antigens but it is unlikely that it has a major impact on the incidence of RBC alloimmunization.

Preventing RBC antibody formation is not practical for most patients and, for many, alloimmunization causes no serious sequelae. However, prevention of RBC alloimmunization is important in women of child bearing age, and for some patients at risk of serious haemolytic transfusion reactions and/or chronic transfusion requirements, e.g., patients with sickle cell anemia.

The administration of Rh Immune Globulin (RhIg) to D-Negative mothers delivering a D- positive infant has been shown to be a highly effective method for reducing the incidence of Hemolytic Disease of the Fetus and Newborn (HDFN) due to anti-D. When RhIg is administered within 72 hours of a full-term delivery of a D-positive infant by a D-negative mother, the incidence of alloimmunization is decreased from 12-13 per cent to 1-2 per cent. When RhIg is also administered at 28 weeks, the incidence of alloimmunization is further decreased to 0.1 per cent. (See Further Reading)

In order to prevent RBC alloimmunization against other RBC antigens, in females at or prior to child-bearing age, for elective surgery likely to require RBC transfusion, autologous rather than allogeneic RBC transfusion should be used if possible. Finally, spouses of women of child-bearing age should not be directed donors for these women (and, in addition, CBS policies do not in any event permit this).

If a D-negative female patient, at or prior to child-bearing age, is transfused with platelets that are either from a D-positive donor or a donor of unknown D status, then an appropriate dose of RhIg should be administered (10-12 µg/mL of transfused RBCs). Some Transfusion Medicine services will administer anti-D to all patients in this circumstance.

For selected high-risk patients with transfusion-dependent diseases such as sickle cell anemia and thalassemia, some transfusion services antigen phenotype patients and provide phenotypically matched donor RBC in an attempt to prevent RBC alloimmunization. There is general agreement that this is useful for Rhesus and Kell blood group antigens but debate exists about its merits for more extensive phenotyping. (See Telen in Further Reading).