What is a Blood Typing Test?
A blood typing test, also known as blood group testing, is a medical procedure used to determine an individual’s blood group. It involves testing the blood sample to identify the presence or absence of certain markers or antigens on the surface of red blood cells. Another important factor in blood typing is the Rhesus (Rh) factor, which determines
whether the blood is Rh positive or Rh negative.
The ABO blood typing method is commonly used for blood grouping. The four main blood types are as follows:
- Type O
- Type A
- Type B
- Type AB
Blood typing is required if there is a need for a blood transfusion or while planning to donate blood. This is because all blood types are not compatible; therefore, knowing the blood group is essential. Moreover, receiving blood that is not compatible with your blood type may result in a severe immunological response.
Why is a Blood Typing Test Done?
Blood group testing is done for several important reasons:
Blood Transfusions and a Transplant
Blood typing is important prior to a blood transfusion and a tissue, organ, or bone marrow transplant to ensure compatibility between the donor’s blood and the recipient’s blood. A mismatch in the blood type can lead to severe transfusion reactions, including blood clumping (agglutination), which can be life threatening.
Pregnancy
Blood typing is done during pregnancy to identify any potential blood type incompatibilities between the mother and the foetus. Incompatibilities can lead to complications such as jaundice and severe anaemia in the new-born, where the mother’s antibodies attack the baby’s red blood cells.
Paternity Testing
Blood typing can be used in paternity testing to determine biological parentage by comparing blood types between potential parents and the child.
Forensic Testing
Blood group testing is used to identify the type of blood from a stained blood sample collected at a crime scene.
Prior to Major Surgeries
In emergency situations where a patient requires an immediate blood transfusion, blood typing is performed to identify the blood group that can be safely administered to the patient.
How is Blood Grouped into Different Blood Groups?
Blood is categorised into different blood groups based on the presence or absence of specific substances. These include:
- Antigens, which are types of proteins and sugars, are present on the red blood cells outer surface
- Antibodies, which are proteins found primarily in plasma (fluid element of the blood)
Every cell possesses a distinct set of antigens or markers on its surface, which allows the immune system of the body to distinguish between the body’s own cells and foreign bodies, such as toxins or bacteria. The immune system is trained to tolerate the body’s own cells but triggers a response upon encountering foreign antigens. This response involves the release of antibodies that bind to the foreign body, flagging it for elimination by other components of the immune system.
In the context of blood cells, if the immune system identifies foreign blood cells (cells that do not match an individual’s blood type) entering the body, for instance, through a blood transfusion, it triggers an immunologic response by producing antibodies against these foreign cells.
The ABO blood typing system and the Rhesus (Rh) type system are the most commonly used systems for blood classification.
ABO blood group system
The ABO blood group system determines blood types based on the presence or absence of specific antigens on red blood cells. The blood group antigens are received from parents.
- Blood type A: Red blood cells possess only antigen A.
- Blood type B: Red blood cells possess only antigen B.
- Blood type AB: Red blood cells have both antigen A and antigen B.
- Blood type O: Red blood cells do not possess either antigen A or antigen B.
The plasma, a liquid component of blood, naturally possesses antibodies against the antigens that are absent on their own red blood cells. Nevertheless, the exact mechanism behind the development of these antibodies without prior exposure to foreign blood types is not fully understood.
- If an individual has blood group A, they will have antibodies against antigen B.
- If an individual has blood group B, they will have antibodies against antigen A.
- If an individual has blood type AB, they will not have antibodies against either antigen A or B.
- If an individual has blood type O, they will have antibodies against both antigens A and B.
Rhesus System
Another widely utilised system for blood typing is the Rhesus (Rh) system, named after its discovery in Rhesus monkeys. In this, the presence or absence of an antigen known as the ‘RhD antigen’ on the red blood cells’ surface determines the blood type. If the RhD antigen is absent, the individual is referred to as Rhesus negative (Rh−). Conversely, if the RhD antigen is present, the individual is considered Rhesus positive (Rh+).
By combining the ABO blood group system with the presence or absence of the Rh antigen, blood can be categorised into eight possible types:
- A negative (A−)
- A positive (A+)
- AB negative (AB−)
- AB positive (AB+)
- B negative (B−)
- B positive (B+)
- O negative (O−)
- O positive (O+)
Universal Recipients and Donors
Ensuring compatibility between the blood you get from a donor and your own blood is crucial for your health and well-being. Incompatibility can lead to severe immunologic responses or even death. Ideally, blood transfusions should come from donors who share the ABO and Rh type same as you. However, in emergency situations, where an exact match is not immediately available, there are alternative blood types that can be compatible, implying they won’t trigger an immune response in your body.
- Individuals with blood type A can receive blood from donors with blood types A and O.
- Individuals with blood type B can receive blood from donors with blood types B and O.
- Individuals with blood type AB can receive blood from donors with blood types A, B, AB, and O (universal recipients).
- Individuals with blood type O can only receive blood from donors with blood type O (universal donors).
Importance of Blood Group Testing in Pregnancy
When parents have different blood types, it does not guarantee that the mother and child will share the same blood type or Rh factor. If the mother has Rh-negative blood and the child has Rh-positive blood, there can be risks during pregnancy and delivery.
During pregnancy, a small number of the foetus’ red blood cells can cross the placenta and enter the mother’s bloodstream. This can lead to the development of anti-RhD antibodies in the mother’s plasma. If these antibodies detect ‘foreign’ antigens in the foetus’ blood cells, they may attack the foetus’ red blood cells as a defensive response.
This can result in severe jaundice and potentially brain damage in the foetus. To prevent this, an injection of anti-RhD immune globulin G may be administered to the mother. This helps prevent the production of the antibody and reduces its impact on the foetus.
Blood testing during pregnancy is crucial in predicting potential risks by determining whether the foetus’ blood type is compatible with the mother’s.
Blood Typing Test
Blood typing procedures are typically conducted at hospitals or clinical laboratories.
Preparation for the test
Blood typing does not require special preparation. If you suspect that you may faint during the test, you should have somebody drive you home after the test.
During the test
- The collection site, usually the arm or hand, is cleansed with an antiseptic solution to ensure a sterile environment and minimize infection risk.
- A technician, applies a band around the upper arm to make the veins more prominent and easier to locate.
- Using a sterile needle attached to a syringe, the technician carefully punctures a vein in the arm or hand and collects a small amount of blood. Multiple samples may be taken for different tests.
- After the blood draw, gauze or cotton is applied to the puncture site. A bandage or adhesive strip is then secured to protect the site and promote healing.
- The collected blood samples are sent to a laboratory for analysis. Skilled laboratory technicians perform the blood typing test.
After the Test
Once the blood typing test is complete, there are typically no specific restrictions to follow. It is recommended to keep the bandage on for a short period to ensure there is no bleeding. In some cases, a minor bruise may appear at the site where blood was drawn.
Results of Blood Typing
After undergoing blood typing, you will receive information about your ABO blood type and whether you are Rh-negative or Rh-positive. The possible results for ABO blood types are:
- Type O
- Type A
- Type B
- Type AB
Based on these results, healthcare providers can determine the compatible blood types you can safely receive:
- If you have type A blood, you can receive blood types A and O.
- If you have type B blood, you can receive blood types B and O.
- If you have type AB blood, you can receive blood types A, B, AB, and O.
- If you have type O blood, you can only receive type O blood.
Additionally, knowing your Rh factor is important:
- If you are Rh-positive (Rh+), you can receive both Rh-positive and Rh-negative blood.
- If you are Rh-negative (Rh-), you can only receive Rh-negative blood.
It is worth noting that type O blood is considered universal, as it can be donated to individuals with any blood type. This is why individuals with type O blood are often referred to as universal blood donors.
Is it Possible to do Blood Group Testing at Home?
It is possible to perform blood typing at home with blood typing kits that are available for purchase. These kits typically include the necessary reagents and instructions to determine your blood type.
To perform an at-home blood typing test, one uses a lancet (a small needle) to prick a cleansed and dried finger. The finger is then lightly squeezed to obtain a few drops of blood, which are placed on specific spots on the provided collection card.
It is crucial to carefully follow the instructions provided with the test kit for both collecting the blood sample and interpreting the results.
It should be noted that the instructions may vary between different test kits, so it is essential to review them thoroughly before proceeding.
Possible Risks of the Blood Typing Test
You must have had your blood drawn for the purpose of having it typed. There are very few risks associated with having your blood collected, including:
- Excessive bleeding from the puncture site
- Hematoma (collection of blood under the skin at the puncture site)
- Feeling lightheaded or fainting
- Puncture site infection
- Multiple punctures to find veins
Takeaway
Blood typing is a procedure that determines a person’s blood group, which falls into one of four main categories: A, B, AB, or O. Each blood group has distinct antigens on the surface of its red blood cells, and antibodies in the blood can attack antigens that are not matches. Blood typing is crucial for determining compatibility in blood transfusions, as receiving incompatible blood can lead to a serious clumping reaction. The procedure is simple and typically performed at a doctor’s office or blood donation centre, with quick results. It carries very few risks and serves as a valuable tool in ensuring the safety and effectiveness of blood transfusions.
