Blood typing

With the help of Blood typing a person can be assigned to a blood group in the A-B-0 or another system. Most frequently, information on the A-B-0 blood group and the Rhesus factor are given when determining blood groups.

What is the blood typing?

There are a number of blood type systems, some of which are now considered obsolete and others are still used to determine the compatibility of the blood of two people. Today's blood group determination is a fixed examination that is regulated in the guidelines of the German Medical Association on hemotherapy.

The blood group in the A-B-0 system and the Rhesus factor are determined. Knowing the blood group is crucial if a blood transfusion is necessary, as certain properties of the donor and recipient blood must match to avoid a potentially life-threatening rejection reaction. In addition, blood grouping is carried out during pregnancy and can be life-saving if a rhesus-negative woman forms antibodies against her rhesus-positive child - a complication that can occur from the second pregnancy.

In patients who have to receive blood transfusions more frequently, the Kell system is also included in the blood grouping. It is important to carry out a blood group determination before an emergency, since after a blood transfusion a determination can be made more difficult by the formation of mixed blood - this also increases the risk of possible complications with further transfusions.

Function, effect & goals

The blood group determination with determination of the Rhesus factor and the A-B-0 blood group is a measure that many patients take voluntarily. If, for example, you are involved in an accident and need medical help, this knowledge can be valuable and save valuable time. The most common uses for blood typing are as follows:

• Prepare for any blood transfusions: before operations or in the event of a physical condition that could make a blood transfusion necessary
• Pregnancy care: preparing for childbirth and detecting a negative Rhesus factor in the mother
• Forensics: Identification of people using known blood group factors (only accompanying other molecular methods)
• Determination of paternity: Blood groups can be inherited, so they can provide initial information when determining biological paternity

Every operation, no matter how small, carries risks, one of which is bleeding and clotting disorders. Although the patient is examined beforehand, profuse bleeding can occur with any operation. In this case, a rapid blood transfusion would be necessary and the time for blood grouping would be missing. Therefore, as a precaution, blood is taken beforehand and tested for blood type and Rhesus factor so that transfusions can be carried out quickly in an emergency.

The same applies to pregnancy; even spontaneous and natural births can lead to heavy bleeding due to injuries or idiopathic causes. In these situations, too, there is no longer enough time to determine the blood group; the woman needs help immediately. If you want to donate blood, the amount to be donated is removed and a small sample from the donor blood is then used to test which blood group it is. The donor is also informed of this, which is often the reason for donating blood. Nowadays, blood grouping is carried out less frequently in forensic medicine.

It used to be used to determine paternity, but was not as certain as today's DNA sample. Fathers who are unsure of biological paternity still have their blood group determined as a first clue, as this is far cheaper than a DNA test - since the blood group is inheritable, it can at least rule out paternity if the child has one Has blood type that it cannot have from the father. Blood grouping can be used in forensic medicine to help identify people, but in recent years and decades it has been increasingly replaced by DNA testing.

Risks, side effects & dangers

A blood grouping is a laboratory test that requests a blood sample from the patient. Only a small amount of blood is withdrawn - unless the blood group determination is used to initiate further examinations at the same time.

A small ampoule with a few milliliters of blood is usually sufficient to determine the blood group. Strictly speaking, the patient does not have to be sober for this and it would even be better for his circulatory system if he wasn't. However, since many doctors do more than just determine the blood group at the same time, they like to order patients to the practice in the morning before breakfast. With the help of a fine injection needle, for example, blood is taken from the crook of the arm, but the patient can also offer any other suitable location. A small bruise can then 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 this is very small and a blood group sample is always taken 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.

In contrast to patients, for whom the blood sample is simply uncomfortable, those affected experience a far greater fear and, in the worst case, blood group determination becomes impossible. 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 clumps after the transfusion.