With the help of blood grouping, a person can be assigned to a blood group in the A-B-0 or another system. Most commonly, blood grouping involves information about the A-B-0 blood group and the rhesus factor.
What is blood grouping?
Knowing the blood group is critical in the event of a necessary blood transfusion, as this requires certain characteristics of the donor and recipient blood to match. There are a number of blood grouping systems, some of which are now considered obsolete and others that are still used to determine the compatibility of two people’s blood. Today’s blood grouping is a defined testing procedure that is regulated in the guidelines of the German Medical Association for hemotherapy. The blood group in the A-B-0 system and the rhesus factor are determined. Knowledge of the blood group is crucial in the event of a necessary blood transfusion, as certain properties of the donor and recipient blood must match in order to avoid a potentially life-threatening rejection reaction. In addition, blood typing is performed during pregnancy and can become lifesaving if a rhesus-negative woman develops antibodies against her rhesus-positive child – a complication that can occur beginning in the second pregnancy. For patients who need to receive blood transfusions more frequently, the Kell system is also included in the blood grouping. It is important to perform blood grouping before an emergency, because after a blood transfusion, determination can be complicated by the formation of mixed blood – which also increases the risk of possible complications with further transfusions.
Function, effect, and goals
Blood grouping with determination of the rhesus factor and the A-B-0 blood group is a measure that many patients have performed voluntarily. If they are involved in an accident, for example, and need medical help, this knowledge can be worth a lot and save precious time. The most common uses for blood typing are as follows:
- Preparing for possible blood transfusions: before surgery or if you have a physical condition that might require a blood transfusion
- Prenatal care: preparation for birth and detection of a negative rhesus factor of the mother.
- Forensics: identification of people using known blood group factors (only accompanying other molecular methods).
- Paternity determination: blood groups are hereditary, so they can provide initial information in the determination of biological paternity.
Any operation, no matter how small it may seem, carries risks, one of which is bleeding and clotting disorders. Although the patient is screened for this beforehand, a severe bleeding can occur during any operation. In this case, a quick blood transfusion would be necessary and there would be no time for blood grouping. Therefore, as a precaution, blood is taken beforehand and tested for blood group and rhesus factor in order to be able to transfuse quickly in an emergency. The same applies to pregnancy; even in spontaneous and natural births, severe bleeding can occur due to injuries or idiopathic causes. Also in these situations, the time for blood grouping is no longer sufficient, the woman needs immediate help. Those who wish to donate blood have it drawn in the quantity to be donated, and a small sample of the donor’s blood is then tested to determine which blood group it is. The donor is also informed of this, which is often the reason for donating blood. Nowadays, blood grouping is performed less frequently in forensic medicine. In the past, it was used to establish paternity, but it was not as reliable as today’s DNA sample. However, fathers who are unsure of biological paternity still have their blood group determined as a first clue, since it is far more convenient than a DNA test – since blood group is hereditary, it can at least rule out paternity if the child has a blood group that it cannot have from the father. For the accompanying identification of persons, blood grouping can be used in forensic medicine, but has been increasingly replaced by DNA testing in recent years and decades.
Risks, side effects and dangers
Blood typing is a laboratory test that requires the patient to have blood drawn. Only a small amount of blood is taken – unless the blood grouping is used to order other tests at the same time. For blood grouping alone, however, a small ampoule containing a few milliliters of blood is usually sufficient. Strictly speaking, the patient does not have to be sober for this and it would even be better for his circulation if he were not. However, since many doctors perform more than just blood grouping at the same time, they like to order patients to come to the practice in the morning before breakfast. Blood is drawn from the crook of the arm, for example, with the help of a fine hypodermic needle, but the patient can also offer any other suitable site. A small bruise may appear at the injection site, which heals within a few days. In this country, infections at the puncture site do not play a role, as the site is very small and a collection for blood grouping is always performed in a sterile environment with prior disinfection of the site. A possible but rare complication can be trypanophobia, in which the patient is afraid of sharp objects and thus also of the small injection needle. Unlike patients for whom blood sampling is merely unpleasant, those affected experience far greater anxiety in this case, and blood grouping becomes impossible in the worst case. Mixing up the blood sample in the laboratory, on the other hand, can be life-threatening if the patient then receives the wrong blood and it clots after transfusion.
