When we donate our blood, it is separated into components - red cells, platelets, granulocytes (white cells) and plasma - to be used in different transfusion treatments.
The Haem-Match project aims to improve treatment by transfusion of red cells, the cells that carry oxygen around the body. When we refer to ‘blood transfusion’ on this website, we are referring to the transfusion of red cells.
Blood transfusion is sometimes required as a one-off, for example if a person loses blood in an accident. In other cases, it may be required regularly over a period of time, for example if a person has blood cancer. Some people, for example those with an inherited anaemia such as sickle cell disorder or thalassaemia, require transfusions every few weeks for very long periods of time.
How We Currently Match Blood
Red blood cells have labels on their surfaces, known as antigens or blood groups.
We inherit our blood antigens genetically from our parents - different people have different sets of blood groups.
Blood is selected for transfusion according to the blood groups of the donor and the blood group of the patient.
A patient may form an antibody against an antigen if the red cells of the donor have an antigen that is ‘foreign’ to the patient i.e. if the red cells of the donor have an antigen that the red cells of the patient do not.
People naturally form antibodies against the A and B blood groups if they do not have them, without being exposed to them through blood, so patients must always be transfused with blood that is matched to be compatible with these types.
The D type is also important so blood is also matched to be compatible with A, B, O and D blood groups.
Antibody formation can be dangerous, because if the patient is transfused subsequently with blood containing the antigen that caused the antibody to form there is a risk that the immune system of the patient will attack the transfused cells,
causing a reaction that can be fatal.
There is a risk of antibody formation each time a person is transfused. Consequently, patients with illnesses that are treated by frequent transfusions (e.g. sickle cell disorder and thalassaemia) are more likely to form antibodies than patients with a condition requiring a one off transfusion (e.g. for surgery). To reduce the risk of antibody formation, blood for regularly transfused patients is matched at present by considering the C, c, E, e and K antigens in addition to the A, B and D antigens.
But could we match even further?
Why Would We Want to Match Further?
Current matching protocols can result in
Patients unnecessarily forming antibodies
Failure to find compatible blood for transfusion
Increased risk of avoidable future harm
Antibodies are particularly common in patients with sickle cell disease and thalassaemia and these can:
- Risk patients becoming untransfusable
Make treatment difficult because there are few alternatives to transfusion
Current selection of blood for transfusion
Is manual, laborious and expensive
Cannot be easily extended to many more blood types
We think that a system that allows us to match many more antigens would be safer for patients.
Haem-Match is a project to develop such a system.