ABO incompatibility
Definition
ABO incompatibility is a reaction of the immune system that occurs if two different and not compatible blood types are mixed together.
Causes
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)
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
Prognosis
This can be a very serious problem which can even result in death. With the right treatment, a full recovery is likely.
Prevention
Careful testing of donor and patient blood types before transfusion or transplant can prevent this problem.