The procedure for determining blood groups according to the ABO system is to detect antigens A and B in red blood cells using standard antibodies and using agglutinins in plasma or serum of the analyzed blood with standard red blood cells. The technique was developed at the beginning of the 20th century and is still actively used in medicine. The determination of antigens A and B is carried out thanks to the anti-A and anti-B cyclones.
Basic concepts
Donors always determine not only antigens in red blood cells, but also agglutinins in serum (plasma) using standard red blood cells. Venous blood is used as biomaterial. Before the study, you must give up fatty foods a day before the analysis and do not smoke half an hour before the test. Blood groups are determined twice: first in the medical department, where the material is procured, and then confirmed by a study in the laboratory.
The determination of blood groups according to the ABO system is the main test that is used in transfusiology. Also, some animals have a similar blood group system, such as chimpanzees, gorillas and bonobos.
Discovery story
In science, there is a generally accepted opinion that the method of determining blood groups according to the ABO system was first discovered by Karl Landsteiner, an Austrian scientist, in 1900. Then he described in his work three types of antigens. For this, thirty years later he was awarded the Nobel Prize in medicine or physiology. Due to the fact that there were no close ties between scientists before, it was later established that the Czech serologist Jan Jansky, regardless of K. Landsteiner's research, first described four human blood groups, but his studies were not known to a wide audience. Currently, it is the classification developed by Y. Yansky that is used in Russia and the republics of the former USSR. In the USA, W. L. Moss created his similar work in 1910.
Methods for determining blood groups according to the ABO system using cyclones
The blood group should be determined in a room with good lighting in compliance with the temperature range from 15 to 25 degrees Celsius, since deviations from this norm can affect the results of the study. The initials and surname of the patient are written on a plate or plate. From left to right or in a circle, the standard designations of the groups (O (I), A (II), B (III)) are applied. The appropriate serum is placed dropwise under them with separate pipettes for each species. Then the patient’s blood is added to them. Material for research is taken from the earlobe or finger. This requires a technique for determining the blood group according to the ABO system.
It is also legitimate to use red blood cells in a test tube after a clot has formed. It is necessary that the amount of serum be more than the amount of blood added ten times. After that, the drops are mixed with glass sticks (separately for each). For five minutes, gently shaking the plate, watch for the appearance of a hemagglutination reaction. It is found in the fact that small red lumps appear, then merge into larger ones. Serum at this time almost completely loses color.
In order to eliminate false hemagglutination of simple gluing of red blood cells, after three minutes you need to add one drop of saline and check whether agglutination persists. If so, then it is true. Everything, the definition of blood groups according to the ABO system is now complete.
Interpretation of Results
As a result, four reactions can be observed:
- agglutination does not occur with any of the sera - the first group O (I);
- the reaction was manifested with sera I (ab) and III (a) - the second group A (II);
- agglutination occurs with sera I (ab) and II (b) - the third group B (III);
- if the reaction occurs with three sera, an additional procedure must be performed with reagents of group AB (IV), which are standard; if there is no agglutination in such a drop, it can be considered that this is the 4th blood group AB (IV).
Express method for Rh factor
The methodology for determining blood groups according to the ABO system involves the simultaneous identification of the Rh factor (Rh).
The surface of the plate is pre-wetted and written on it "control serum" and "serum antiresus". Then, one or two drops of the necessary reagents are placed under the inscriptions and the analyzed material is added to them. For this, you can also use blood from the finger (in the same amount as the volume of the serum) or red blood cells remaining at the bottom of the tube after the appearance of a clot (half the volume of the serum). The choice of material does not affect the final result. Then the blood and serum are mixed with a dry glass rod, after which the reaction is expected for five minutes. In order to eliminate false readings, after three to four minutes add an isotonic sodium chloride solution (only a few drops). Determination of blood group according to the ABO and Rh system is carried out very often.
If erythrocyte agglutination in a drop with serum occurs, this indicates a positive rhesus blood. According to statistics, Rh + is found in 85% of the world's population. Its absence allows us to talk about Rh negative affiliation. If agglutination appeared in the control serum, then it became unusable. Unfortunately, the algorithm for determining the blood group according to the ABO system does not always work perfectly.
What mistakes can be made with this technique?
Inaccuracies in determining blood belonging to a particular group depend on the following reasons:
- Technical.
- Biological specificity of the studied blood.
- Defective character of standard sera and red blood cells.
Technical errors
Possible errors in determining the blood group of the ABO system in a cross way:
- Incorrectly located serum plate.
- Incorrect quantitative proportions of the material.
- Use of insufficiently clean plates or plates that come in contact with blood (each serum should be collected with a separate pipette, washed with a solution of sodium chloride (at a concentration of 0.9%)).
- Incorrect record of the analyzed material.
- Non-observance of the time required for the onset of agglutination - you should not rush and take into account the reaction before five minutes have passed, because there may be weak agglutinogens in the blood. Overexposure is also not worth it, because the drops can dry from the edges and lead to a false conclusion. It is important to follow the rules for determining the blood group according to the ABO system.
- Erroneous centrifugation can also lead to a false result.
- Exceeding air temperature affects the absence of agglutination. To avoid errors of this kind, you need to use a special serum designed to work in hot climates. It is necessary to determine blood groups on a plate or plate, the outer surface of which falls into cold water.
Biological specific errors
Errors associated with the biological specificity of the analyzed blood are divided into two types.
- Dependent on the characteristics of red blood cells.
- Errors due to biological characteristics of serum.
Consider each view in more detail.
Red blood cell dependent
- Late agglutination due to "weak" forms of red blood cells and antigens. In order to avoid errors, it is necessary to determine the blood group of donors and recipients using standard red blood cells. Agglutinogen A 2 should be identified by repeated testing with other types of reagents and other dishes, increasing the reaction time.
- “Panagglutination” (“autoagglutination”) - the ability of blood to exhibit the same reaction of a non-specific nature with all serums, including their own. After five minutes, the severity of such agglutination weakens, although it should increase. Similar cases are observed in cancer patients, burned, etc. As a control, it is necessary to evaluate the manifestation of agglutination of the analyzed red blood cells in standard serum of the fourth group and saline. When "panagglutination" blood group is determined as a result of triple washing of red blood cells. If it does not give the desired result, it is worthwhile to re-take the blood sample in a test tube warmed up before the procedure and put the sample in a thermal container to help maintain a temperature of 37 degrees Celsius and above. Then it should be delivered to the laboratory, where the above temperature is stored and heated saline solution, plate and reagents are used.
- Sometimes the red blood cells of the analyzed blood are located as "coin columns", and they can be mistaken for agglutinates. If you add two drops of an isotonic solution and gently shake the tablet, the red blood cells are in the right position.
- Incomplete or mixed agglutination, which occurs in patients with the second, third and fourth groups as a result of bone marrow transplantation or in the first three months after blood transfusion 0 (I).
Due to the biological characteristics of serum
- During routine testing, antibodies of a different specificity are detected as a result of previous sensitization. It is necessary to determine it and select red blood cells without the antigen to which immunization has been detected. The recipient must necessarily select compatible donor blood individually.
- There are no antibodies A and B, which is observed in newborns and patients suffering from inhibition of humoral immunity.
- During the formation of “coin columns”, the abnormal result must be confirmed by taking standard red blood cells of the first group. The sodium chloride solution and the rocking of the tablet help to differentiate between real agglutinates and “coin columns”.
Errors associated with the use of defective standard red blood cells and sera
Weak sera with a past shelf life or having a titer of less than 1:32 are capable of generating weak and late agglutination. The use of such reagents is unacceptable.
The use of unsuitable standard red blood cells or sera prepared under non-sterile conditions and insufficiently preserved, leads to the appearance of "bacterial" agglutination, which is of a non-specific nature.
There are many popular assumptions about the blood groups of the ABO system, which appeared immediately after its discovery in different world cultures. So, for example, in the 30s of the last century in Japan and some other countries, a theory that connected a blood group with a particular type of personality gained popularity. Similar theories are popular today.
There is also an opinion that a person with group A is prone to a severe hangover, O is associated with good teeth, and group A2 is associated with the highest level of IQ. But scientifically such claims are not proven.
We examined the determination of blood groups according to the ABO system using standard sera.