Difference Between ABO and Rh Blood Grouping System

The key difference between ABO and Rh blood grouping system is that ABO blood grouping system is based on the presence or absence of the antigens A and B on the surface of the red blood cells, while Rh blood grouping system is based on the presence or absence of the Rh antigen (Rh factor) on the cell membranes of the red blood cells.

ABO and Rh blood grouping systems classify blood groups based on the presence and absence of antigens on the red blood cell membranes. ABO blood grouping system considers the presence and absence of A and B antigens, while Rh blood grouping system considers the presence and absence of Rh antigens. ABO system is the most important blood grouping system used to match the blood type of donor and receiver in transfusion medicine. Rh system is the second most important blood grouping system.

CONTENTS

1. Overview and Key Difference
2. What is ABO Blood Grouping System
3. What is Rh Blood Grouping System
4. Similarities Between ABO and Rh Blood Grouping System
5. Side by Side Comparison – ABO vs Rh Blood Grouping System in Tabular Form
6. Summary

What is ABO Blood Grouping System?

ABO blood grouping system classifies blood groups based on the presence of one, both or neither of the A and B antigens on erythrocytes (red blood cells). This blood grouping system was discovered by Karl Landsteiner in 1901. According to the ABO blood grouping system, a person may carry type A, type B, type O, or type AB blood. Once this system was identified, blood transfusions became safer. The blood type O does not express A or B antigens, while the blood type AB expresses both A and B antigens. The blood type B expresses B antigens while blood type A expresses A antigens. A single gene called ABO gene located on chromosome 9 at 9q34.1-q34.2 codes for ABO blood groups. It has three main allelic forms: A, B, and O.

ABO system is used to match the blood type of donor and receiver in blood transfusions. People with O blood group are considered universal donors since they can donate blood to anyone. People with AB blood group can accept blood from any donor. Hence, they are universal recipients. People with type A or B can receive the matching blood or type O blood.

What is Rh Blood Grouping System?

Rh blood grouping system is the second most important blood grouping system after the ABO system. It is based on the presence and absence of Rh factor or immunogenic D-antigen on the red blood cell membranes. If the Rh antigen is present, the blood type is Rh positive. When the Rh factor is absent, the blood type is Rh negative.

There are more than 50 defined antigens in the Rh blood grouping system. However, D antigen is one of the greatest concerns. Other important antigens are C, c, E, and e. Two linked genes; RhD and RhCE code for Rh antigens. Rh factor is the main cause of hemolytic disease in newborns (HDN).

What are the Similarities Between ABO and Rh Blood Grouping System?

• ABO and Rh blood grouping systems classify blood groups based on antigens present on red blood cells.
• Both systems are used during the blood transfusion.

What is the Difference Between ABO and Rh Blood Grouping System?

ABO blood grouping system is the most important blood group system which classifies blood groups based on the presence and absence of A and B antigens on red blood cells. On the other hand, Rh blood grouping system is the second most important blood group system that classifies blood groups based on the presence and absence of Rh antigens on red blood cells. So, this is the key difference between ABO and Rh blood grouping system. Moreover, a single gene named ABO gene codes for antigens of ABO system, while the two linked genes, RhD and RhCE, code for Rh antigens. Thus, this is another significant difference between ABO and Rh blood grouping system.

The below infographic tabulates the difference between ABO and Rh blood grouping system for side by side comparison.

Summary – ABO vs Rh Blood Grouping System

ABO blood grouping system is the most important blood-group system in transfusion medicine. This system classifies blood groups based on the presence and absence of A and B antigens on the surface of red blood cells. There are four types of blood groups (A, B, AB and O) in the ABO system. Rh blood grouping system is the second most important blood grouping system. It is based on the presence and absence of Rh antigen on the red blood cell membranes. If the Rh factor is present, an individual is rhesus positive (Rh+ve). If the Rh factor is absent, the individual is rhesus negative (Rh-ve). Thus, this is the summary of the difference between ABO and Rh blood grouping system.

Reference:

1. Dean, Laura. “The ABO Blood Group.” Blood Groups and Red Cell Antigens [Internet]., U.S. National Library of Medicine, 1 Jan. 1970, Available here.
2. Dean, Laura. “The Rh Blood Group.” Blood Groups and Red Cell Antigens [Internet]., U.S. National Library of Medicine, 1 Jan. 1970, Available here.

Image Courtesy:

1. “ABO blood type” By InvictaHOG – Own work (Public Domain) via Commons Wikimedia

2. “Rh blood cells drawing” By Sophiedionne14 – Own work (CC BY-SA 4.0) via Commons Wikimedia