Blood group AB+ (positive) or AB- (negative): definition, differences and distribution

Blood group AB+ (positive) or AB- (negative): definition, differences and distribution

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Blood group AB is the least common in Europe. What are its characteristics ? Who should donate blood to based on their rhesus? Answers from Dr Syria Laperche, medical director of the French Blood Establishment (EFS).

What are the different types of blood groups?

A blood group is determined by the presence or absence of certain antigens on the surface of red blood cells: antigens A and B belonging to the ABO system and antigen D belonging to the Rhesus system. This antigenic system is hereditary. Blood group determination makes it possible to determine blood compatibility or incompatibility between two individuals. In total, there are more than thirty blood systems with more than 350 antigens. The best known are the ABO system, discovered in 1900 by the American biologist and doctor Karl Landsteiner, and the Rhesus (Rh) system which can be positive or negative. In Europe, 85% of people are Rh positive and 15% Rh negative.

In practice, the ABO system offers four possibilities for antigen expression: group A, group B, group AB and group O. “Each individual has antibodies against blood groups that they do not have. Thus, subjects with blood group A have anti-B antibodies. Those in group B have anti-A antibodies, those in group O have anti-A and anti-B antibodies, and those in group AB have neither of these antibodies”, develops Dr Syria Laperche.

The ABO and Rhesus systems can give eight possible combinations:

  • Blood group A negative (A-);
  • Blood group A positive (A+);
  • Blood group B negative (B-);
  • Blood group B positive (B+);
  • AB negative blood group (AB-);
  • AB positive blood group (AB+);
  • Blood group O negative (O-);
  • Blood group O positive (O+).

Blood group AB+ or AB-: what are the differences?

Why is AB+ a universal receiver?

“AB+ and AB- people have the same blood group (AB) but not the same Rhesus (positive or negative). The red blood cells of AB+ subjects are covered with A and B and Rhesus positive antigens on their surface. group AB have neither anti-A antibodies nor anti-B antibodies which destroy group A and group B red blood cells. Individuals with blood group AB are therefore considered to be universal receiversthis means that they can receive red blood cells of any ABO blood group.”indicates the specialist.

Which blood group is AB- compatible with?

The red blood cells of individuals in groups A, B or O have anti-B, anti-A or anti-A and anti-B antibodies. Also, group AB blood cannot be transfused to them at the risk of causing hemolysis of the red blood cells. Therefore, group AB blood can only be transfused to group AB subjects. On the other hand, they can receive blood from any other group since they have neither anti-A antibodies nor anti-B antibodies.

Is blood type AB rare or common?

Blood group AB is the least represented in Europe. According to the French Blood Establishment, only 4% of the population owns the AB group. Among these individuals, 3/4 are rhesus positive and 1/4 rhesus negative.

Distribution of blood groups in Europe according to the French Blood Establishment:

  • A positive: 38% of the population;
  • O positive: 36% of the population;
  • B positive: 8% of the population;
  • A negative: 7% of the population;
  • O negative: 6% of the population;
  • AB positive: 3% of the population;
  • B negative: 1% of the population;
  • AB negative: 1% of the population.

Blood group O negative (O- blood): the universal donor

The red blood cells of O- people have no antigen on their surface. Therefore, they can be transfused to all blood groups. This is the reason why individuals in the O- group are considered universal donors.

Group AB+ or AB-: how and why to know your blood group?

The blood group card is usually obtained after the birth of the child, in which case it is kept in the health record. If the examination has not been carried out or the card has been lost, the analysis can be carried out using a simple blood test.

There are two main situations in which it is important to know your blood type:

  • At the start of pregnancy to ensure that there is no rhesus incompatibility between the mother and the fetus. An incompatibility could endanger the vital prognosis of the fetus;
  • In a transfusion context: surgical intervention with risk of hemorrhage, severe anemia or emergency.

When donating blood, blood grouping is carried out in order to know the blood group of the donor, and then avoid any problem of blood incompatibility at the time of transfusion.

“However, in a life-threatening emergency with massive bleeding, group O- can be transfused to anyone because there is no risk that the transfused person will develop antibodies. But, in the majority of cases, patients are transfused with blood from a donor of their own blood type”, reassures the specialist.