ABO incompatibility

Answer 1

Definition

ABO incompatibility is a reaction of the immune system that occurs if two different and not compatible blood types are mixed together.

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.

Answer 2

Definition

ABO incompatibility is an immune system reaction that occurs when blood from two different and incompatible blood types are mixed together.

See also: Transfusion reaction - hemolytic

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 (one A and one B molecule)
• 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
• A patient with type AB blood will NOT react against type A, type B, or type AB blood

Because type O does not have any surface molecules, type O blood does not cause an immune response based on ABO incompatibility. 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 ABO incompatible transfusion reactions:

• Back pain
• Blood in urine
• Feeling of "impending doom"
• Fever
• Yellow skin (jaundice)

Signs and testsThe health care provider will perform a physical exam. Blood tests will usually show:

• Bilirubin levelis high
• Complete blood count (CBC) shows damage to red blood cells or anemia
• The patient's and donor's blood 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 (intravenously)
• Medicines to raise blood pressure if it drops too low

Expectations (prognosis)

ABO incompatibility can be a very serious problem that 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 symptoms of ABO incompatibility.

Prevention

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

References

Goodnough L. Transfusion medicine. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 183.

Wu YY, Mantha S, Snyder EL. Transfusion reactions. In: Hoffman R, Benz E Jr, Shattil S, et al, eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Churchill Livingstone; 2008:chap 153.

Reviewed By

Review Date: 08/24/2011

David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.