Blood is represented by 36 known blood group systems. The ABO group and Rh group are the most important and familiar blood group systems for blood transfusion.
The ABO group determines the blood group (A, B, O, or AB) of a person, whereas the classification of positive (+) or negative (-) blood of an individual is specifically determined by RHD gene of the Rh group.
The essential difference between positive (+) and negative (-) hinges on the presence or the absence of the RHD gene. Commonly known blood groups are created by the ABO group and the Rh group.
Blood donor at donation. Image Credit: May Preechaya / Shutterstock
When a patient requires a single blood transfusion, they can be given blood only based on the ABO group and the Rh group. In contrast, when a patient requires multiple blood transfusions, they need to be given extensively matched blood.
When determining the most suitable blood group for the patients, subtypes of all the blood group systems are taken into consideration. Only based on the ABO group and the Rh type, a donor can give blood when there is a requirement for blood transfusion. In some cases, some patients may require ongoing multiple blood transfusions for the rest of their lives.
For instance, if a patient has blood loss due to surgery, he will be transfused with red blood cells. The red blood cells are also used in treating anemia.
The platelets transfusion is carried out to treat cancer patients as they tend to lose healthy cells during the process of radiation or chemotherapy. Also, people who are affected by burns need plasma transfusions.
‘Dce’ is produced by combining RHCE and RHD genes, which is also called as the Ro subtype. It could also be assumed from the 'Dce' that if someone has the Ro subtype, they would have the RHD gene and thereby a positive blood group. It signifies that for the people with the Ro subtype, they always have either A+, B+, AB+, or O+ blood type.
Management of sickle cell disease is an example of a need for ongoing, regular transfusions. Ideally, the Ro subtype blood should be given to the Ro subtype patient with sickle cell disease. Ro blood is rare among the donors.
O Rh negative blood can be given to any patient regardless of the blood type, which made it very essential. Commonly, donors with the B Rh positive blood group are found in ethnic communities of Black and south Asian minority.
Rare Blood Types
If an individual's blood has rare antigens or lacks common antigens, then their blood type is considered rare. It purely depends on what is presented in the blood along with the ABO types, and the Rhesus positive or negative determines the rare type. The presence and absence of antigens A and B determine the four major blood groups.
- Blood group A – It contains antigens A on the red blood cells with anti-B antibodies in the plasma.
- Blood group B – It contains antigens B on the red blood cells with anti-A antibodies in the plasma.
- Blood group AB – It contains antigens A and B but antibodies are absent.
- Blood group O – Antigens are absent but it contains both anti-A and anti-B antibodies in the plasma.
During transfusion, there are many methods followed for safe matching of the blood type.
- The universal donor, O blood group, donates blood cells to the antibodies.
- A and AB blood types are supplied with red blood cells by group A.
- B and AB blood types are supplied with red blood cells by group B.
- Group AB receives blood cells from all the groups but can donate only to AB blood types.
Apart from antigens A and B, there is another one called Rh factor which is of two types: positive and negative, depending on its availability. The blood from Rh negative individuals can be given to the Rh negative patients, whereas the blood from both Rh negative and positive can be given only to the Rh positive patients. The blood type O negative is found in the universal red cell donor. The blood type AB is found in the universal plasma donor.
Acquiring the Blood Type
The blood type of an individual is inherited just like the color of the eyes and hair. Finding an exact match for the blood type of rare kind is a difficult task. It may cause severe side effects if less matched blood is given. Hence, it is always advised to give the patients the best suitable blood. Every individual will not be aware of their blood types and subtypes. But individuals with rare blood group should share their blood group details with donors if they belong to the same ethnic heritage.
So, we are aware that we need numerous donors from the black heritage for treating patients with sickle cell disease, and we need donors who are primarily from Asian, Mediterranean, or Arab heritage for patients with thalassaemia. Blood with a certain combination of genes is the Ro subtype. Only 2% of the donors have Ro subtype, which has led the donors to be valued highly.