Your blood group is determined by the genes that you inherit from your parents. There are four main blood groups and these include: A, B, AB and O. In addition, each group can either be RhD positive or RhD negative, which means that there are 8 blood groups in total. About 85% of the UK population is RhD positive and 36% of the population is O+ which is the most common blood type. Of these eight blood types, the rarest is AB negative and just 1% of donors have it. Despite this being rare the demand for AB negative blood is low and in general there is no struggle finding donors with AB negative blood.
Regarding the Rh group, it is comprised of two genes RhD gene and RHCE gene. The RhD gene can either be present therefore positive or absent therefore negative. The RHCE gene is more complex and can result in four different variations: c, C, e, E. So when the two different genes come together there are eight different possible antigen combinations and these were discovered by American scientist Alexander Wiener in 1943. When the RhD gene and RHCE gene combine it can produce Dce, which we call the Ro subtype. As it contains D it must be positive therefore people with the Ro subtype will always have to be A+, B+, AB+ or O+ regarding the blood type.
As I previously mentioned the rarest blood type currently: AB negative is not in high demand therefore does not cause much problem however there are some blood types which are unfortunately both rare and in demand. This includes the Ro subtype, which is often used to treat people with sickle cell.
The Ro subtype is a variation of the Rh positive blood type and everyone has a blood subtype so having the Ro subtype does not mean there’s a problem with your blood. The two main reasons that the Ro subtype is particularly important are that the demand is increasing by 10-15% each year and only 2% of regular donors have the Ro subtype.
Sickle cell is a group of hereditary blood disorders that cause red blood cells to become sickle, which is a half-moon shape. This makes it harder for the red cells to move around the body and they can stick together, blocking blood vessels. Symptoms of sickle cell include excruciating pain, anaemia and organ damage. Anyone can have sickle cell, but it most commonly affects people from black African or black Caribbean backgrounds. Regular blood transfusions every 4 to 6 weeks are one of the ways to prevent or relieve the symptoms of sickle cell. In recent years more and more people with sickle cell have started having red cell exchange transfusions. The process removes the person’s red blood cells and replaces them with those from donors. This requires much more blood than other types of transfusion so the demand for blood has increased. A stem cell or bone marrow transplant is the only known cure for sickle cell.
When a patient requires a blood transfusion, they can usually be given blood from a donor based on their ABO group and Rh type only. With some medical conditions, however, patients can require on-going multiple blood transfusions, sometimes for the rest of their lives. These patients need to be given more extensively matched blood. So, if a patient has the Ro subtype and requires on-going multiple transfusions, usually they need blood of the Ro subtype. Receiving blood from the wrong ABO group can be life threatening. For example, if someone with group B blood is given group A blood, their anti-A antibodies will attack the group A cells. This is why group A blood must never be given to someone who has group B blood and vice versa. As group O red blood cells do not have any A or B antigens, it can safely be given to any other group.
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