What is an ABO incompatibility reaction?

An ABO incompatibility reaction can occur if you receive the wrong type of blood during a blood transfusion. It’s a rare but serious and potentially fatal response to incompatible blood by your immune system.

These reactions are extremely rare, because doctors are aware of the danger of using the wrong blood during a transfusion. There are many precautions in place to reduce the chances of a mistake. Your doctor and nurse know to look for certain symptoms during and after your transfusion that might mean you’re having a reaction. This allows them to provide you with treatment as quickly as possible.

Learn more: Transfusion therapy »

The four main blood types are A, B, AB, and O. If you’re type A, your red blood cells have proteins attached to them known as A antigens. Type B blood cells carry B antigens. Type AB blood has both A and B antigens, and type O blood has neither A nor B antigens.

Your immune system will produce antibodies against any blood antigens you don’t have in your own blood. That means people with type A blood create antibodies against B antigens. A person with type A blood receiving a transfusion of type B or AB blood would have an ABO incompatibility reaction. In an ABO incompatibility reaction, your immune system attacks the new blood cells and destroys them.

If you have type AB blood, you have both A and B antigens. This means you’re a universal recipient and you can receive any type of blood. However, you can only donate blood to other people who have type AB blood.

If you have type O blood, which has no antigens, you’re a universal donor. You can give your blood to anyone without triggering their immune system, but you can only receive type O blood.

Before a blood transfusion, your doctor will test your blood to determine your blood type. A small sample will be crossmatched with some of your donated blood. The two samples of blood are then mixed and watched for a reaction. This allows your doctor to be certain an incompatibility reaction won’t take place.

Human error is the most likely cause of an ABO incompatibility reaction. If your transfusion uses the wrong blood type, it could be the result of mislabeled blood, incorrectly completed forms, or a failure to check donated blood before the transfusion.

If you have an ABO incompatibility reaction, you’ll have symptoms within a few minutes of receiving a transfusion. These may include:

Medical staff will stop the blood transfusion if they suspect you might be having an incompatibility reaction. They’ll tell the blood bank about it, because there’s a risk that the wrong blood could also have been given to other patients.

Learn more: Transfusion reactions »

Your doctor will test samples of your blood for evidence of destruction of your red blood cells. They’ll also test your urine to see if it contains hemoglobin, a component released from broken-down blood cells. They’ll double-check your blood type and carry out the crossmatch procedure again.

While these procedures are performed, your doctor or nurse will monitor your vital signs, including your:

You may need to enter the intensive care unit. After stopping your blood transfusion, the medical staff will attach a saline drip to the line to keep it open.

The goal of treatment is to prevent you from having kidney failure, extensive blood clotting, and blood pressure that’s abnormally low. You may receive oxygen and intravenous fluids. You may also receive a drug to increase your urine output. If you’re at risk of having widespread clotting, you may receive a transfusion of plasma or platelets.

There isn’t much that patients can do to prevent ABO incompatibility reactions. However, most hospitals and blood banks have systems in place to reduce the chance that such a reaction will occur. These include:

  • checking the identities of donors to ensure that their details match the information on their blood samples
  • correctly labeling stored samples
  • double-checking the blood type of both patients and blood packs before each transfusion

During an ABO incompatibility reaction, the red blood cells inside your circulatory system break down. Blood clotting may occur throughout your body, shutting off the blood supply to vital organs or causing a stroke. Too much blood clotting can use up clotting factors and leave you at risk of excessive bleeding.

Some of the products released from broken-down blood cells can cause kidney damage and possibly kidney failure. An ABO incompatibility reaction can be life-threatening unless your doctor successfully treats it right away. However, if you have a reaction and receive the correct treatment without delay, you should recover completely.