ABO incompatibility

• Causes, incidence, and risk factors

  A, B, and O are the three major blood types. The types are based on small substances (molecules) on the surface of the blood cells. In people who have different blood types, these molecules act as immune system triggers (antigens).

  Each person has a combination of two of these surface molecules. Type O lacks any molecule. The different blood types are:

  • Type A (AA or AO molecules)
  • Type B (BB or BO molecules)
  • Type AB
  • Type O

  People who have one blood type form proteins (antibodies) that cause their immune system to react against other blood types. Being exposed to another type of blood can cause a reaction. This is important when a patient needs to receive blood (transfusion) or have an organ transplant. The blood types must be matched to avoid an ABO incompatibility reaction.

  For example:

  • A patient with type A blood will react against type B or type AB blood
  • A patient with type B blood will react against type A or type AB blood
  • A patient with type O blood will react against type A, type B, or type AB blood

  Because type O lacks any surface molecules, type O blood does not cause an immune response. This is why type O blood cells can be given to patients of any blood type. People with type O blood are called "universal donors." However, people with type O can only receive type O blood.

  Since antibodies are in the liquid part of blood (plasma), both blood and plasma transfusions must be matched to avoid an immune reaction.

• Symptoms

  The following are symptoms of transfusion reactions:

  • Back pain
  • Blood in urine
  • Feeling of "impending doom"
  • Fever
  • Yellow skin (jaundice)
• Signs and tests
  • Bilirubin level is high
  • Complete blood count (CBC) shows damaged red blood cells, may also show mild anemia
  • Lab testing of patient's and donor's blood shows that they are not compatible
• Treatment

  Treatment may include:

  • Drugs used to treat allergic reactions (antihistamines)
  • Drugs used to treat swelling and allergies (steroids)
  • Fluids given through a vein (intravenous)
  • Medicines to raise blood pressure if it drops too low
• Expectations (prognosis)

  This can be a very serious problem which can even result in death. With the right treatment, a full recovery is likely.

• Complications
  • Kidney failure
  • Low blood pressure needing intensive care
  • Death
• Calling your health care provider

  Call your health care provider if you have recently had a blood transfusion or transplant and you have the symptoms listed above.

• Prevention

  Careful testing of donor and patient blood types before transfusion or transplant can prevent this problem.

• References

  McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: Saunders; 2006.

  Hoffman R, Benz E, Shattil S, Furie B, Cohen H. Hematology: Basic Principles and Practice. 4th ed. Philadelphia, Pa: Churchill Livingstone; 2004.

Review Date: 5/13/2008

Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.