Blood Grouping And Typing: A Guide for Africans


By Foluke Akinwalere. Freelance Health Writerr. With medical review and editorial support by the DLHA Team.


Blood groups

Blood grouping and typing.  Image credit by atiwat2610 on Freepik






In the realm of healthcare, the significance of blood transfusion cannot be overstated. Whether in emergencies, surgical procedures, or chronic medical conditions, the availability of compatible blood plays an important role in saving lives.


At the core of this life-saving practice, lies the intricate science of blood grouping and typing. This article delves into the crucial role these processes play in ensuring the successful and safe administration of blood transfusions. 




What are blood groups and blood types?


Blood group is a classification of blood, based on the presence or absence of specific antigens on the surface of red blood cells. In the case of red blood cells groups, the antigens are sugars that are attached to specific components on the cell membrane. The most well-known blood group system is the ABO system, which classified blood into four main groups.  A, B, AB, and O


Blood type is a more general term that encompasses the blood group and additional characteristics of the blood such as the Rh factor, which categorised blood as Rh-positive or Rh-negative based on the presence or absence of the Rh factor (or protein called antigen).


Therefore, blood type includes information about the ABO group and the Rh factor which now create the 8 most common blood types; A+, A-, B+, B-, AB+, AB-, O+, and O-


Blood group and type are inherited genetically from your parents. Whether your blood group is type A, B, AB or O is based on the blood types of your mother and father and it is important for you to know your blood type as part of your health record.




Understanding the ABO System and Rh Factor


ABO blood system


The 4 main blood groups, A, B, AB, and O are determined by the genes you inherited from your parents.


They are identified by antibodies and antigens in the blood.  


Antibodies are proteins found in plasma that are part of your body’s natural defenses. They alert your immune system of foreign substances such as germs, which destroy them.


Antigens are protein molecules found on the surfaces of red blood cells.  These are based on the presence or absence of specific antigens on the surface of a red blood cell. Individuals with type A blood have A antigens, type B has B antigens, type AB has both A and B antigens, while type O lack both A and B antigens. 



  • Blood group A — has A antigens on the red blood cells and B antibodies in the plasma
  • Blood group B — has B antigens on the red blood cells and A antibodies in the plasma
  • Blood group AB — has both A and B antigens on the red blood cells but no antibodies in the plasma
  • Blood group O — has no antigens on the red blood cells but both A and B antibodies are in the plasma


Rhesus (Rh) D Factor 


Rhesus (Rh) or RhD factor is another important blood group system It is an inherited protein that is found on the surface of the red blood cell. It is the positive (+) or negative (-) sign next to the blood groups.


If your blood type is positive, then your blood cells have the RhD protein


If your blood type is negative, then your blood cells lack the RhD protein


Having a Rh-negative blood type does not indicate illness and usually does not affect your health.


The Rh factor is used to indicate whether the blood of two different people is compatible when mixed — for example, the blood of a mother and her baby at birth.


There are no concerns if an expecting mother is Rh negative and her baby is Rh negative.  But if the expecting mother is Rh negative and her baby is Rh positive, the mother’s blood might produce antibodies which will affect the development of the unborn child, who is Rh positive, and can lead to complications.




Who are Universal Donors and Universal Receivers?


Universal Donors


Type O negative (O-) individuals are considered universal donors because their blood lacks A, B, and RhD antigens, which minimise the risk of reactions in receivers. It can be used in transfusion for any blood type. However, the need for O-negative blood is the highest because it is used most often during emergency situations.


Universal Receivers


AB-positive (AB+) individuals are universal receivers because they can receive blood from any ABO or RhD type without adverse effects. 


Identifying universal donors and receivers aids in emergencies when immediate transfusions are necessary.




What is Crossmatching in Transfusion?


Crossmatching involves mixing a small sample of the donor’s blood with the receiver’s blood to assess compatibility beyond ABO and Rh typing. It is done before a blood transfusion is performed.


It is a trial version of a transfusion to ensure that specific antibodies in the receiver’s blood do not react with antigens in the donor’s blood. It is done to prevent immune responses and transfusion reactions.




How is Blood Typing Conducted In Case of Emergency?


If the blood type of an emergency patient is known at the time of admission for care, immediate and rapid blood typing can be conducted promptly in order to initiate life-saving transfusion without delay.


But in cases when the patient’s blood type is unknown, the person can receive type O-negative red cells without producing an ABO or RhD incompatibility reaction.



Importance of Blood Compatibility in Transfusion


A compatibility chart for the ABO blood system as shown in figure 1 is a reference tool used in transfusion medicine to determine the compatibility between blood donors and receivers based on the ABO blood groups.

Blood compatibility chart

Click on image to enlarge.


Blood transfusions must adhere to specific compatibility rules to prevent some common adverse effects. These are based on the interaction of antigens and antibodies present in the donor and recipient blood.


Blood transfusion compatibility follows these general rules:

  • Type A individuals can receive blood from A or O donors
  • Type B individuals can receive blood from B or O donors
  • Type AB individuals can receive blood from A, B, AB, or O donors (universal receivers)
  • Type O individuals can receive blood only from O donors (universal donors).


Rh Factor Consideration


In addition to ABO compatibility, the Rh factor (positive or negative) must also be considered. Rh-positive individuals can receive Rh-positive or Rh-negative blood, while Rh-negative individuals can receive only Rh-negative blood to prevent Rh incompatibility reactions.




What Are the Risks of Blood Mismatch in Transfusion?


The risk of mismatched transfusions in the ABO system can lead to serious consequences.  In some cases, it can lead to organ failure, particularly the kidney,  and even death due to reactions between antibodies and the antigens of the mismatched red blood cells. 


If incompatible blood is given in a transfusion, the donor cells are treated as if they are foreign invaders, and the receiver’s immune system attacks them and destroys them accordingly.




How To Reduce the Risk of Adverse Reactions To Blood Mismatch


To reduce the risk of adverse reactions arising from blood mismatch, healthcare professionals must follow the following rigorous protocols and safety measures:

  • Ensure precise blood typing of both the donor and receiver to match the ABO and Rh systems
  • Perform a crossmatch test before the transfusion to verify compatibility between the donor’s blood and the receiver’s blood
  • Ensure that healthcare professionals involved in blood transfusions are well-trained and updated on the latest safety protocols
  • Equip healthcare facilities with emergency response plans in case of severe adverse reactions
  • Conduct regular audits and quality assurance checks to assess transfusion practices’ effectiveness and identify improvement areas.


Understanding and applying the principles of the ABO blood system compatibility chart and Rh factor consideration are essential in preventing immune reactions and ensuring the safety of blood transfusions.




Emphasising the critical role of blood grouping and typing in transfusion safety is very important.  With thorough comprehensive blood typing, healthcare professionals can minimise the potential for adverse reactions, ensuring that transfused blood is compatible with the receiver’s immune system. The importance of universal donors and receivers underscores the need for a systematic approach to blood typing, especially in emergency situations where rapid interventions are crucial. Emphasis on accuracy and efficiency in blood typing contributes significantly to the overall safety and success of transfusion practices.






NHS Blood Groups  [Internet. Last reviewed on 10 May, 2023]. Accessed January  16, 2024.

American Red Cross Facts About Blood and Blood Types [Internet. N.d.] Accessed January  16, 2024.

American Red Cross What Is The Rh Factor? Why Is It Important? Internet. June 28, 2023.] Accessed January 17, 2024.

Rudlof B, Just B, Deitenbeck R, Ehmann T. Mismatched transfusion of 8 AB0-incompatible units of packed red blood cells in a patient with acute intermittent porphyria. Saudi J Anaesth. 2011 Jan;5(1):101-4. doi: 10.4103/1658-354X.76497.

NIH. National Library of Medicine. National Center for Biotechnology Information. Blood Groups and Red Cell Antigens [Internet. N.d.] Accessed January 21, 2024.

American Society of Hematology Blood Safety and Matching [Internet. N.d.] Accessed January 23, 2024.


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Published: January 26, 2024

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