In a blood grouping, a determination of the AB0 blood group as well as a rhesus determination is performed. In addition, an antibody screening test is also performed.
The AB0 system describes blood group antigens that are found on the blood cells (erythrocytes (red blood cells), leukocytes (white blood cells), platelets (blood platelets)). The blood group antigens A, B, O can be distinguished. From these, the blood groups can be derived:
- O – frequency ~ 40%
- A – frequency ~ 40 %
- B – frequency ~ 10 %
- AB – frequency ~ 4 %
In blood groups A and AB, we can again distinguish subgroups in relation to the A (A1 and A2), which differ in quantity. In the AB0 system, antibodies occur against the antigens A, B, O, which are located around blood plasma. In each case, IgM antibodies are present in the blood plasma of a person, which do not lead to agglutination (clumping) of the person’s own blood cells.
If a transfusion of blood from a foreign blood group occurs, an antigen-antibody reaction occurs (ABO incompatibility), in which agglutination of the erythrocytes occurs.
The Rhesus system describes antigens on the erythrocytes (red blood cells). The following antigens can be distinguished:
- C, c
- D, d
- E, e
Approximately 85% of the population is rhesus positive. In contrast to the ABO system, IgG antibody formation occurs only after immunization.
Both systems was described in the 20th century by Karl Landsteiner.
This blood group system has special significance for obstetrics, but must also be taken into account for blood transfusions or organ transplants.
In the meantime, prenatal RhD diagnosis is possible by analysis of cell-free circulating DNA of the fetus from maternal plasma, so that the Rh status of a fetus can be determined at an early stage and a decision can be made as to whether Rh prophylaxis is necessary.
In addition to these, other blood group systems can be distinguished:
- Duff system
- Kell system ~ 92% of people are Kell negative (kk).
- Kidd system
- Lewis system
The procedure
Material needed
- Whole blood
Preparation of the patient/performance
- A sample and a counter sample are performed to achieve the greatest possible certainty in the determination
- Sample: erythrocytes of the patient are tested against ABO antibodies and rhesus antibodies.
- Counter sample: blood serum of the patient is tested against erythrocytes of blood groups A, B, O.
Interfering factors
- Blood grouping is complicated in the presence of heat and cold antibodies due to interference with autoantibodies.
Indications
- Blood grouping prior to surgery, during pregnancy or paternity testing.
- Pre-testing before the administration of blood products.
- Forensic examinations
