ABO Incompatibility Reaction

What is An ABO Incompatibility Reaction?

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

These reactions are extremely rare, as doctors are very aware of the danger of using the wrong blood during a transfusion. There are many precautions in place to reduce the risk of a mistake. However, if a reaction does occur during or after a transfusion, doctors and nurses know what symptoms to look for. This allows them to provide treatment as quickly as possible.

Understanding Blood Type

There are four main blood types, known as A, B, AB, and O. If you are 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.

Normally, your immune system will produce antibodies against any blood antigens you do not have in your own blood. That means type A people create antibodies against B antigens, and a transfusion of type B or AB blood would lead to an ABO incompatibility reaction. In other words, if you received B or AB blood, your immune system would attack the new blood cells and destroy them.

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

If you have type O blood, which has no antigens, you are a universal donor. Your blood can be given to anyone without triggering their immune system, but you can only receive type O blood.

Normally, before a blood transfusion, your blood will be tested to determine your blood type and a small sample will be cross-matched with some of the donated blood. During a cross match, the two samples of blood are mixed and viewed under a microscope. This allows doctors to make certain an incompatibility reaction wont take place.

Causes and Risk Factors

Human error is the most likely cause of an ABO incompatibility reaction. If the wrong blood type is used during a transfusion, it might be the result of mislabeled blood, incorrectly filled out forms, or a failure to check donated blood before the transfusion.


Should a reaction occur, you would normally experience symptoms within a few minutes of receiving a transfusion. These may include:

  • a strong feeling that something bad is about to happen
  • fever and chills
  • breathing difficulties
  • muscle aches
  • feeling nauseous
  • chest pains, abdominal pain or back pain
  • pain where the transfusion line is inserted
  • blood in your urine
  • jaundice

Diagnosis and Tests

As soon as medical staff suspects that you might be experiencing an incompatibility reaction, they will stop the blood transfusion. The blood bank will be informed, as there is a risk that the wrong blood could also have been given to other patients.

Doctors will test samples of your blood for evidence that your red blood cells have been destroyed and also test your urine to see if it contains hemoglobin, a component released from broken-down blood cells. They will double-check your blood type and carry out the cross match procedure again.

While these procedures are carried out, a doctor or nurse will monitor your vital signs such as your blood pressure, heart rate, breathing, and temperature.


You may be admitted to an intensive care unit. After stopping your blood transfusion, the medical staff will attach a saline drip to the line in order to keep it open.

Treatment is aimed at preventing you from developing abnormally low blood pressure, kidney failure, and extensive blood clotting. You may be given oxygen, fluids will be administered into your vein, and you may have a drug to increase your urine output. If you are in danger of experiencing widespread clotting, you may receive a transfusion of plasma or platelets.


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, leaving you at risk of excessive bleeding.

Some of the components released from broken-down blood cells can cause kidney damage and possibly kidney failure. An ABO incompatibility reaction can be fatal unless doctors successfully treat it straight away.

However, if you have a reaction, and are given the correct treatment without delay, you should recover completely.


There is not 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 donors identities to ensure that their details match the information on their blood samples
  • correctly labeling stored samples
  • double checking blood type of both patients and blood packs before each transfusion