QotW: Can transfusions change your blood type?

It’s time for Question of the Week, and Emma Hildyard has been searching for an answer to this vital question from Mark...

Emma - Hmmm… interesting question. We put it to our forum. Polly didn’t think it was possible, Chris and Evan said you need a bone marrow transplant to change your blood type. So we asked Dr Cedric Ghevaert from the University of Cambridge.

Cedric - Our blood cells are divided into red cells, white cells and platelets. All our blood cells carry an identity card on their surface made out of different proteins or sugars: we call these blood groups.

The most important and well known blood group is the one carried by the red cells and it can be O, A, B or AB combined.

Emma - When doctors need to give someone a blood transfusion, they try to match the blood group of the red cells in the new blood with the red cells in the patients’ blood - so, you’d give type A blood to someone who has type A blood in their body. This is important because otherwise the new blood cells would be destroyed very quickly by the patient’s immune system and cause a really serious reaction. But in an emergency, you might not have bags of the exact blood group to hand…

Cedric - In hospital, emergency departments and surgical theatres will have access to “emergency” blood packs that can be accessed very quickly for people who are bleeding and need blood urgently. And this is O blood.

The O blood group is the most common. O cells can be given to all patients.

I had a patient who was group A and had a very big bleed after delivering her baby. She had to have 76 packs of blood over a period of 8 hours, most of those were group O. Each pack replenishes about half a litre of blood and an adult has on average 5 litres of blood. This patient basically bled her whole blood volume 7 times over! By the time the bleed was under control, she had bled all her own A cells and she only had the O transfused cells. So we basically changed her blood group!

But, that change was only temporary: over the following three to four weeks the transfused O red cells gradually disappeared and were replaced by her own newly produced A cells. That situation is very different from people who have regular small transfusions for example when they have leukaemia: two or three packs of red cells every two to three weeks. In those cases we match the blood and do not replace the whole blood volume several times over.

So to answer your question, can we change a blood group with transfusion. Yes, we can, but only in very rare emergency situations.

Emma - Thanks for that Cedric. There’s always chance to be-positive about these things. Next time we’ll be answering a question from Alex:

Alex - I have several friends with huskies, who claim that the thick fur of the dog protects them not only from the cold but from a hot summers days as well. Could this possibly be true?