Jump to Main Content


Blood Groups and Compatibility Testing: Learning Objectives


Medical Importance

Recipients of red cell transfusions may have (or may form) antibodies to donor red cells. Such serological incompatibility is important because transfusion of incompatible blood can kill people. In fact, acute intravascular hemolytic reactions due to ABO incompatibility of the donor and recipient are the leading preventable cause of transfusion-related death. Serological incompatibility of the recipient and donor can also result in hemolytic disease of the newborn and delayed hemolytic transfusion reactions, both of which can result in morbidity and mortality.


  1. Be able to name the four major blood types (phenotypes) in the ABO system.
  2. Be able to name the two main "naturally occurring" antibodies to red cell antigens.
  3. Be able to tell which of these two antibodies would be found in individuals of each ABO type, and briefly explain why ordinarily they would or would not be present.
  4. Be able to explain why the ABO system is the most important red cell blood group system for transfusion therapy.
  5. Given the Rh phenotype of a mother and her fetus, be able to state whether the baby may be at risk of developing hemolytic disease of the newborn (HDN) due to anti-Rh antibodies, and why (or why not). Be able to state the immunoglobulin class responsible for HDN, and give the reason that other classes of immunoglobulin do not cause HDN.
  6. Be able to diagram the direct antiglobulin test (the Coombs test), indicating the main components and their source (patient vs. reagent). Be able to state what the direct antiglobulin test is capable of detecting. Be able to diagram the indirect antiglobulin test and state the major purpose for the indirect antiglobulin test.
  7. Be able to list the three essential steps in blood compatibility testing, and the purpose of each step.
  8. In an emergency situation, be able to indicate what kind of blood is given, if necessary, before typing is complete, and what kind of blood is given, if necessary, before cross-matching is complete.