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What are Blood Groups?
A blood group is a way to categorize the type of blood a person has. Our blood differs from person to person, based on the presence (or absence) of certain molecules on the surface of red blood cells. These substances, usually proteins in nature, are called antigens. There are a large number of blood group systems, although we’ll concentrate on two of the well-known systems in this article.
What are common blood groups?
An individual’s blood group is determined by the presence of components (called antigens) on the surface of their red blood cells. While there are more than 100 blood groups identified todate, the ABO and Rh blood group systems are the major ones
ABO Blood Group Sytem
The ABO blood group system was discovered way back in —- and is the most important. This system is dependent on the presence or absence of either Antigen A or B, both or none of them form the surface of red blood cells
If A or B antigen is present, then that person has blood group A or B respectively. if both And B are present, then the person’s blood group is AB. However if an individual’s red blood cell do not express either Ao r B antigen, then that person’s blood group is O.
The table below summarises the ABO blood groups as determined by the presence of red cell A or B antigen.
Its important to note the ABO system is further subdivided into smaller subgroups. For example, group A has A1 and A2 subgroups
The RH system
The second most important blood group system is the Rh system. This blood group is determined by the presence or absence of D antigen on the red blood cell. When present, it’s designated as Rh+ and Rh- when absent.
The ABO and Rh systems are usually tested and reported together. So, blood group, A person will be designated group A+ when Rh antigen is present and A- when it’s absent. The same applies to B, AB, and O blood groups.
| Red Blood cell Antigen | Antibody in plasma | Blood Group | RH present | Rh Absent |
|---|---|---|---|---|
| A | b | A | A+ | A- |
| B | a | B | B+ | B- |
| AB | None | AB | AB+ | AB- |
| None | a,b | O | 0+ | 0- |
From the table above we can see there are 8 blood groups in the ABO/RH system.
What Determines Blood Group?
The type of blood group a person has is determined by inheritance. Both the mother and father contribute genes that eventually determine the child’s blood group.
Blood Grouping and Cross-Matching
Blood group testing is usually carried out by the blood transfusion unit (BTU, blood bank) or within the haematology section of a medical laboratory. To find out someone’s blood group, the procedure is outlined below
Blood Grouping – Determining blood type in the laboratory
blood is mixed with various antisera (see image on the right). After mixing, agglutination/clot formation is checked. The well with agglutination indicates the presence of a particular antigen
Crossmatching
This refers to the mixing of a drop of blood of the recipient with a compatible donor ( i.e. same ABO Rh group) to check for agglutination. This step ensures the blood does not contain other less frequent antigens that may cause incompatibility in the recipient.
Why and when blood grouping is done
Several reasons require an individual to have their blood group test tested. These include:
🩸New mothers attending ANC for the first time. Checking a mother’s blood is a part of the AnteNatal Care Profile panel that you can read more about here.
🩸Newborns – In some countries, babies are blood-typed immediately after birth.
🩸Blood donation and transfusion. During blood donation, the donor must have their blood group checked. Conversely, a recipient of blood or blood products must have their blood group known to them to ensure they receive compatible blood.
🩸Persons undergoing surgery. As part of pre-operative preparation, the patient’s blood group should be known in case an emergency transfusion is required during surgery.
🩸Travel – some countries require travellers’ blood group
🩸Joining college, military training, or other select jobs eg emergency services, etc.
🩸Any person who wants to know their blood group.
Where To Have Your Blood Group Tested.
Everyone needs to be aware of their blood group. In Kenya, Most hospitals, medical centres, and laboratories perform blood typing tests.
The cost of blood grouping may vary but it’s typically between KES300 -800. At our facility in Kilimani, the blood grouping is available at Kes 450
💡You can know your blood group for free when you go to donate blood!
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