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Of the many existing antigens in medical practice The greatest importance is given to three types of blood agglutinogens. One of them is the type responsible for the manifestation of the Rh factor: if it is present on the erythrocyte membrane, the blood group is diagnosed as Rh+, if absent - Rh-. If erythrocytes with Rh+ agglutinogens enter the Rh-negative blood, the body triggers an immune response and begins to produce antibodies to this antigen, which causes pathological conditions.

REFERENCE! The Rh factor is a complex multicomponent system of several dozen antigens. The most common of them are agglutinogens type D (85% of cases), as well as E and C.

The Coombs test is performed only if there is direct evidence. General list of reasons for prescribing the Coombs test:

  • planning and management of pregnancy (parents have different Rh);
  • donation and preparation for blood transfusion (blood mismatch according to Rh is no less destructive than mismatch according to the AB0 system);
  • planned surgical intervention(in case of replenishment of blood loss with blood transfusion);
  • diagnosis of hemolytic diseases.

More specific indications depend on the type of study being performed.

Direct Coombs test

The direct test detects antibodies on the surface of red blood cells. This is necessary to diagnose existing hemolytic pathologies:

  • autoimmune (red blood cells and hemoglobin are destroyed as a result of an attack by the body’s own antibodies);
  • medicinal ( pathological process starts accepting some medicines such as quinidine or procainamide);
  • post-transfusion (if the blood type does not match during transfusion), as well as in the form of Rh conflict during pregnancy (erythroblastosis of newborns).

REFERENCE! Hemolytic anemia is a disease associated with the premature destruction of red blood cells as a result of hemolysis, which leads to insufficient oxygen saturation of the blood and hypoxia of the brain and/or internal organs.

Hemolysis of blood elements is observed in oncological, infectious, rheumatic diseases, therefore the direct Coombs test can be used as additional remedy diagnostics pathological condition. It is worth remembering: negative meaning analysis does not exclude the possibility of hemolysis, but is a reason for additional examination.

Indirect Coombs test

Indirect testing is more often used to prevent pathological situations. It helps to detect antibodies in blood plasma, which is necessary for assessing transfusion compatibility and diagnosing the risks of Rh conflict during pregnancy.

More than 80% of people have a positive Rh factor (Rh+), respectively, just under 20% are Rh negative. If an Rh- mother develops an Rh+ child, her body begins to produce antibodies that attack the red blood cells of the fetus, causing hemolysis.

Taking into account the fact that the percentage of “different rhesus” marriages reaches 12-15%, the risk of hemolytic disease of newborns should be high, but in reality, only in 1 out of 25 such cases, women experience the phenomenon of sensitization (for 200 successful births there is 1 example of hemolytic pathology). This is partly due to the fact that the first Rh-positive child usually does not cause open aggression from the mother’s body; The overwhelming majority of cases occur in the second and subsequent children. The same principle applies as with conventional sensitization to a particular allergen.

There is no reaction upon first contact. The body is just getting acquainted with a new antigen, producing antibodies of the IgM class, which are responsible for a rapid immune response, but rarely penetrate the placental barrier into the child’s blood. All pathological reactions appear upon a second “meeting”, when the body begins to produce IgG class antibodies that easily penetrate the fetal bloodstream, starting the process of hemolysis.

Indirect Coombs test during pregnancy allows you to detect the presence of antibodies in the mother’s body and identify in time initial stage sensitization. A positive answer requires registration with a monthly antibody titer test and mandatory hospitalization 3-4 weeks before birth.

REFERENCE! Rh factor incompatibility does not affect the mother's condition in any way, hemolytic disease develops only in a child. In severe cases and in the absence of a timely response, the fetus may die in the womb or immediately after birth.

Preparation for the procedure and its implementation

Venous blood is used for diagnosis. No special long-term preparation is required for the Coombs test. Try to follow a standard set of rules before taking blood from a vein for analysis:

  • give up alcohol for 3 days, medications(if possible);
  • Plan your last meal later than 8 hours before taking blood for analysis;
  • give up smoking, physical, mental and emotional stress within 1 hour;
  • Before the procedure, drink a glass of clean still water.

The research method is based on the hemagglutination reaction.

When performing a direct test a blood sample is exposed to pre-prepared antiglobulin serum with known indicators, the mixture is kept for some time and checked for agglutinates, which are formed when antibodies are present on red blood cells. The level of agglutinates is diagnosed using the agglutinating titer.

Indirect sample Coombs has a similar technique, but a more complex sequence of actions. Antigenic erythrocytes (with Rh factor) are introduced into the separated blood serum, and only after these manipulations antiglobulin serum is added for diagnosis and agglutinate titer.

Research results

Normally both straight and indirect Coombs test should give a negative result:

  • a negative direct test indicates that specific antibodies to the Rh factor associated with red blood cells are absent in the blood and cannot cause hemolysis
  • a negative indirect test shows that there are also no free antibodies to the Rh factor in the blood plasma; this fact indicates the compatibility of the donor’s blood with the recipient’s blood (or the blood of the mother and child) according to the Rh factor.

A positive Coombs test indicates the fact of Rh sensitization of the body, which is main reason Rh conflict in case of blood transfusion or when carrying a child with a different Rh status. In this case, the results remain unchanged for 3 months (the lifespan of red blood cells). If the cause is autoimmune hemolytic anemia, then a positive test can follow the patient for several years (in some cases, throughout his life).

REFERENCE! The antiglobulin test is highly sensitive, but has little information content. It does not record the activity of the hemolytic process, does not determine the type of antibody and is not able to identify the cause of the pathology. To get a more complete picture, the attending physician must prescribe additional research(blood microscopy, general and biochemical analysis, rheumatic tests, ESR, iron and ferritin levels).

The degree of sensitization can be expressed qualitatively (from “+” to “++++”) or quantitatively in the form of a titer:

  • 1:2 - low value, not dangerous;
  • 1:4 - 1:8 - the beginning of the development of an immunological reaction; does not pose a danger, but requires constant monitoring;
  • 1:16 -1:1024 - a strong form of sensitization, immediate action should be taken.

Reason positive test I can be:

  • transfusion of untyped blood (or with a typing error), when the Rh factor of the donor and recipient do not match;
  • Rh conflict during pregnancy (if the composition of blood antigens in the father and mother do not match);
  • autoimmune hemolytic anemia - both congenital (primary) and secondary, which is a consequence of certain diseases (Evans syndrome, infectious pneumonia, syphilis, cold hemoglobinuria, lymphoma);
  • drug hemolytic reaction.

None of the above problems can be solved by the patient without medical care. In all cases, urgent consultation, registration or emergency hospitalization will be required.

ATTENTION! In rare cases, a false-positive Coombs test is possible. The reason for this can be frequent blood transfusions, as well as a number of diseases: rheumatoid arthritis, lupus erythematosus, sarcoidosis. This phenomenon can also be observed after removal of the spleen, as well as when the reaction is disrupted (frequent shaking of the contents, the presence of contaminants).

Hemolytic anemia, caused by autoimmune bodies that are directed against their own red blood cells, are not precisely understood. However, it is assumed that some factors (for example, a virus, an abnormal protein) change red blood cells in such a way that the body perceives them “as something foreign” and fights them with the help of antibodies. According to another theory, antibodies directed against red blood cells arise almost accidentally during the formation of abnormal plasma protein bodies in some diseases. Such protein bodies, just as “randomly,” can give reactions that can be used to make a diagnosis (for example, viral pneumonia, as is known, gives a positive Wasserman reaction, a positive Paul-Bunnel reaction and a cold agglutination reaction).

There are two main types of autoantibodies for hemolytic anemia, namely: warm antibodies (react at 37°C) and cold antibodies (the reactivity of which increases as the temperature approaches zero). Warm antibodies are more common than cold antibodies. Dacie found that warm hemolysins occur 2 times more often than cold ones. Hemolysins and agglutinins are not fundamentally different antibodies: they differ only in the nature of their action. Agglutinins agglutinate red blood cells, and hemolysins make them more susceptible to the complex process of hemolysis (complement!). Autoantibodies, fixing on erythrocytes, form an erythrocyte-globin complex. This complex is detected using the Coombs antiglobin test.

Coombs test carried out with Coombs serum, for the preparation of which the rabbit is sensitized with human serum, against which antibodies are formed in the rabbit serum. When such a sensitized serum acts on human erythrocytes, their agglutination occurs if the erythrocyte receptors are occupied by blocking antibodies. Since these blocking antibodies are derived from human serum, they agglutinate with rabbit serum sensitized to human plasma and containing precipitins. This reaction is called the Coombs test; For hemolytic anemia on the basis of autoimmune bodies (Lo tit) it is almost specific (for details, see Maier).

In general for hemolytic anemias with a primary disorder of erythrocytes, the Coombs test is negative, and with acquired ones, it is positive. However, there are some exceptions to this rule: a false-positive Coombs test was found during crises of constitutional hemolytic anemia, and in weak degree- also sometimes after splenectomy, with rheumatic arthritis, sarcoidosis, after frequent blood transfusions and with systemic lupus erythematosus. Naturally, in acquired hemolytic anemia without the formation of autoimmune bodies, it is negative.

Hemolytic anemia caused by autoimmune bodies can be divided into:
a) acute, subacute and chronic forms, as well as on
b) idiopathic with unknown etiology and c) symptomatic [viral pneumonia (cold agglutinins only), chronic lymphatic leukemia, reticulosarcoma, lymphosarcoma, systemic lupus erythematosus (mainly warm, less often cold agglutinins), syphilis (cold agglutinins), ovarian tumors (Miescher with employees)).
c) symptomatic [viral pneumonia (cold agglutinins only), chronic lymphatic leukemia, reticulosarcoma, lymphosarcoma, systemic lupus erythematosus (mainly warm, less often cold agglutinins), syphilis (cold agglutinins), ovarian tumors (Miescher and co-workers)).

Clinic of hemolytic anemia, developing under the influence of autoimmune bodies, is very diverse, and therefore it is hardly possible to draw their general clinical picture. Persons of all ages and both sexes are equally affected. Still, idiopathic forms seem to be more often observed in women (Sacks and Workman).

Clinical picture of the idiopathic form varies depending on the severity of the disease. IN chronic cases The onset is gradual, the disease drags on for many years with frequent exacerbations. The severity of anemia varies depending on the degree of hemolysis. Drops in hemoglobin up to 10% are observed; in other cases, hemoglobin remains at 50-60% for a long time. The intensity of reticulocytosis and icteric coloration of the skin and serum corresponds to the degree of hemolysis. Bilirubin is very rarely found in urine, since it does not pass through the kidneys, but hemoglobinuria is observed. In chronic cases, the spleen is often enlarged and can even reach a very significant size, but in other cases it can still be felt. The liver is rarely not enlarged.

In the blood in most cases macrocytosis is observed, in acute stages there are also many microcytes, normoblastosis and polychromasia are rarely absent, leukocytosis can reach 30,000, platelets are normal. In some cases, however, there is severe thrombocytopenia. Evans explains these cases by the simultaneous presence of antibodies against platelets, so that there is both hemolytic anemia and thrombocytopenia due to the action of autoimmune bodies - Evans syndrome. Osmotic resistance is slightly reduced, but not to the same extent and not as permanently as in constitutional globular cell anemia. Heat resistance test (Hegglin-Maier) after 6 hours can also give slight hemolysis (own observation), but to a lesser extent than for Marchiafava anemia. Hemosiderin is also found in urine (own observation).

Coombs test

Coombs test– an antiglobulin test aimed at identifying in Rh-negative blood incomplete anti-erythrocyte antibodies to the Rh factor - a specific protein that is located on the surface of the erythrocytes of Rh-positive blood. There are two types this test: direct – detection of antibodies on the surface of red blood cells, indirect – detection of antibodies in blood serum. Direct testing is carried out in the diagnosis and monitoring of treatment of blood diseases: hemolytic anemia, hemolytic disease of newborns and others. An indirect test is performed to assess the compatibility of the blood of the donor and recipient during transfusion, as well as to determine the presence and risk of Rh conflict when planning and managing pregnancy. The material for the Coombs test is deoxygenated blood, the study is carried out using methods based on the agglutination reaction. Normally, both tests give a negative result. The analysis is completed within one day.

Coombs test – clinical trial Rh-negative blood, aimed at detecting antibodies to the Rh factor. The test is used to identify the risk of developing Rh conflict and hemolytic reactions. In each person, the surface of red blood cells contains a certain set of antigens or agglutinogens - compounds of various natures, the presence or absence of which is used to determine the blood type and Rh factor. There are many types of antigens, in medical practice the largest practical significance have agglutinogens A and B, which determine the blood group, and agglutinogen D, which determines the Rh factor. With a positive Rh factor, D antigens are detected on the outer membrane of erythrocytes, but with a negative factor, they are not.

The Coombs test, also called the antiglobulin test, is aimed at detecting incomplete anti-erythrocyte antibodies to the Rh factor system in the blood. Antibodies to the Rh factor are specific immunoglobulins that are produced in Rh-negative blood when red blood cells with agglutinogens D enter it. This can happen when the blood of the fetus and the pregnant woman is mixed, during blood transfusions carried out without prior blood typing. The Coombs test exists in two versions - direct and indirect. When performing a direct Coombs test, antibodies attached to the surface of red blood cells are detected. The study is used to determine the cause of the hemolytic reaction. The indirect Coombs test is aimed at detecting anti-erythrocyte antibodies in blood plasma. It is necessary to determine the compatibility of blood between donor and recipient or mother and fetus, and helps prevent the development of Rh conflict and subsequent hemolysis of red blood cells.

Blood for both versions of the Coombs test is taken from a vein. The analysis is performed by agglutination using antiglobulin serum. The results of the study are used in hematology to identify the causes of hemolytic reactions, in surgery and resuscitation when conducting blood transfusions, in obstetrics and gynecology when monitoring pregnancies in women with Rh-negative blood.

Indications

The direct Coombs test, which detects antibodies attached to the surface of red blood cells, is prescribed for hemolytic reactions (destruction of red blood cells) of various origins. The study is indicated for primary autoimmune hemolytic anemia, post-transfusion hemolytic anemia, hemolytic disease of the newborn, hemolysis of erythrocytes caused by autoimmune, tumor or infectious diseases, as well as reception medicines, for example, quinidine, methyldopa, procainamide. The indirect Coombs test, which determines antibodies in blood plasma, is used to prevent the development of Rh conflict. It is indicated for patients in preparation for blood transfusions, as well as for pregnant women with negative Rh factor provided that the future father of the child has a positive Rh factor.

To determine Rh compatibility, the Coombs test is not prescribed to patients with Rh-positive blood. In these cases, there are already antigens on the surface of red blood cells; the production of antibodies cannot be provoked by blood transfusion or the entry of fetal blood into the bloodstream of the pregnant woman. Also, the study is not indicated for pregnant women if both parents have a negative Rh factor - an inherited recessive trait. The child in such couples always has Rh-negative blood; an immunological conflict with the mother is impossible. In hemolytic pathologies, the antiglobulin test is not used to monitor the success of therapy, since the results do not reflect the activity of the process of destruction of red blood cells.

A limitation of the Coombs test is the laboriousness of the research procedure - to obtain reliable results, it is necessary to comply with temperature and time conditions, rules for the preparation of reagents and biomaterial. The advantages of the Coombs test include its high sensitivity. In hemolytic anemia, the results of this test remain positive, even if the hemoglobin, bilirubin and reticulocyte levels are normal.

Preparation for analysis and collection of material

The material used to perform the Coombs test is venous blood. There are no special requirements for the time of the blood sampling procedure and for the preparation of the patient. As with any study, it is recommended to take a break after eating for at least 4 hours, and stop smoking in the last 30 minutes. physical activity, avoid emotional stress. It is also worth discussing with your doctor in advance the need to stop taking medications - some drugs can distort the results of the Coombs test. Blood is taken using a syringe from the cubital vein, less often from the vein on back side brushes Within a few hours, the material is delivered to the laboratory.

When performing a direct Coombs test, antiglobulin serum is added to the patient's blood serum. After some time, the mixture is examined for the presence of agglutinates - they are formed if there are antibodies on the red blood cells. If the result is positive, the agglutinating titer is determined. The indirect Coombs test consists of more steps. First, antibodies present in the serum are fixed on the injected red blood cells during incubation. Then antiglobulin serum is added to the sample, after some time the presence and titer of agglutinates is determined. The analysis period is 1 day.

Normal results

Normally, the result of the direct Coombs test is negative (-). This means that there are no antibodies associated with red blood cells in the blood, and they cannot cause hemolysis. Normal result The indirect Coombs test is also negative (-), that is, there are no antibodies to the Rh factor in the blood plasma. When preparing for blood transfusion for the recipient, this means compatibility with the donor’s blood; when monitoring pregnancy, this means the absence of Rh sensitization of the mother, a low risk of developing an immunological conflict. Physiological factors, such as dietary habits or physical activity, cannot affect the test result. Therefore, if the result is positive, a doctor’s consultation is necessary.

Diagnostic value of the analysis

Positive result The Coombs test is expressed qualitatively, from (+) to (++++), or quantitatively, with titers from 1:16 to 1:256. Determination of the concentration of antibodies on red blood cells and in blood serum is performed in both types of samples. If the direct Coombs test is positive, antibodies are detected on the outer membrane of red blood cells, which lead to the destruction of these blood cells. The cause may be blood transfusion without prior typing - post-transfusion hemolytic reaction, as well as erythroblastosis of the newborn, hemolytic reaction due to the use of drugs, primary or secondary autoimmune hemolytic anemia. Secondary destruction of red blood cells can be caused by systemic lupus erythematosus, Evans syndrome, Waldenström macroglobulinemia, paroxysmal cold hemoglobinuria, chronic lymphocytic leukemia, lymphoma, infectious mononucleosis, syphilis, mycoplasma pneumonia.

A positive result of the indirect Coombs test indicates the presence of antibodies to the Rh factor in the plasma. In practice, this means that Rh sensitization has occurred, and there is a possibility of developing Rh conflict after infusion of donor blood during pregnancy. To prevent pregnancy complications, women with a positive Coombs test result are placed on a special register.

Treatment of abnormalities

The Coombs test refers to isoserological studies. Its results make it possible to identify a hemolytic reaction, as well as determine the compatibility of the blood of the donor and recipient, mother and fetus, in order to prevent the development of Rh conflict. If the test result is positive, then you need to seek advice from your attending physician - obstetrician-gynecologist, hematologist, surgeon.

Antiglobulin test, or Coombs test This is done to identify certain antibodies that attack red blood cells (erythrocytes).

Antibodies are proteins produced by the immune system. Typically, antibodies bind to foreign substances such as bacteria and viruses and destroy them.

2. Why is an antibody test needed?

An antibody test may be performed in the following cases:

Before blood transfusion

You probably know that a person can have one of four blood types. And an antiglobulin test can be performed to determine the possibility of blood transfusion. If you are receiving a transfusion, the donor's blood must match your type (have the same antigens). If the antigens are different during transfusion, the immune system will destroy the transfused cells. This may lead to serious illnesses and even death. This is why finding the right blood type is so important.

To identify the risk of Rh sensitization

Rhesus is an antigen. Its full name is Rh factor. The Coombs test is used to detect antibodies to the Rh factor in the blood of pregnant women. If a woman with negative Rh blood is pregnant with a child with a positive Rh factor (it can be passed on from the father), there is a risk of Rh sensitization. Rh sensitization occurs when the baby's blood mixes with the mother's blood during pregnancy or childbirth. If the mother's blood type is incompatible with the baby's blood type, then her immune system may attack the fetus, perceiving it as a foreign object. In this case, it may develop serious disease, called erythroblastosis fetalis. In rare cases, if the disease is not treated, the fetus or newborn may die.

A woman with Rh negative blood may be given an injection of anti-Rh gammaglobulin (eg, RhoGAM), which is used to prevent the development of Rh hemolytic disease.

For the diagnosis of autoimmune hemolytic anemia

Autoimmune hemolytic anemia is rare disease associated with the formation of antibodies to self-antigens of erythrocytes.

3. Types of antiglobulin test

There are two types of antiglobulin test, or Coombs test: direct and indirect.

Direct Coombs test or direct antiglobulin test detects antibodies bound to red blood cells. It is used to determine anemia. In this disease, red blood cells are destroyed faster than they are produced.

Indirect Coombs test, or indirect antiglobulin test carried out to search for antibodies not associated with red blood cells. The test uses blood serum, which contains antibodies. This procedure is quite rare: it is mainly performed to determine the possibility of a blood transfusion or as a stage of examination of pregnant women.

4. Results of the Coombs reaction

Norm:

Negative test result - no antibodies detected.

  • Direct Coombs test. A negative direct antiglobulin test means your blood does not have antibodies associated with red blood cells.
  • Indirect Coombs test. A negative indirect antiglobulin test result means that your blood is compatible with the donor's blood. For a pregnant woman, this result means that her body has not produced antibodies against the Rh-positive blood type of her child (Rh-sensitization has not occurred).

Deviation from the norm:

  • Direct Coombs test. A positive direct antiglobulin test means your blood has antibodies that fight against red blood cells. This may be caused by a transfusion incompatible blood or diseases such as hemolytic anemia or hemolytic disease of the newborn (HDN).
  • Indirect Coombs test. A positive indirect antiglobulin test means that your blood is incompatible with the donor's blood. In a pregnant woman, such results mean the presence of antibodies against the positive Rh factor of the child's blood (Rh sensitization). If the baby has a positive Rh blood factor, the mother will be closely monitored by a doctor throughout the pregnancy.

Apply 1 large drop of serum O(I), A(II), B(III) onto a plate or glass slide using pipettes (different!). After noting the time, use a clean glass rod or a clean corner of a glass slide to combine drops of serum with drops of blood. The determination lasts 5 minutes, shaking the plate, then add 1 drop of saline solution to each mixture of drops and evaluate the results. It is better if the serum comes in 2 different series. The blood group results must match in both serum lots.

Evaluation of isohemagglutination results:

    isohemagglutination. If the reaction is positive, tiny red grains of adhesive red blood cells appear in the mixture. The grains merge into larger grains, and the latter into flakes. The serum is almost discolored;

    if the reaction is negative, the mixture remains uniformly colored for 5 minutes pink color and no grains are found;

    When working with 3 sera of groups O(I), A(II), B(III), 4 combinations of reactions are possible:

    1. if all 3 sera gave a negative reaction, that is, the mixture is uniformly colored pink - this is O(I) blood type;

      If negative reaction only serum of group A(II) gave, and sera O(I) and B(III) gave a positive reaction, that is, grains appeared - this is A(II) blood group;

      serum of group B(II) gave a negative reaction, and sera of group O(I) and A(II) gave a positive reaction - this is B(III) blood group.

    all 3 serums gave positive reactions- test blood AB(IV) group. In this case, a study is carried out with AB(IV) group serum.

Note! Drops of the blood being tested should be 5-10 times smaller than drops of serum.

Isohemagglutination errors.

Failure to perform agglutination where it should be and presence of agglutination where it should not be. This may be due to a weak serum titer plus poor red blood cell agglutination.

Presence of agglutination where there should not be any- This is pseudoagglutination, when piles of red blood cells form “coin columns”. Shaking the plate or adding saline destroys them.

Panagglutination, when serum sticks together all red blood cells, including those of its own blood type. By the 5th minute, signs of agglutination disappear.

There is also the so-called cold panagglutination, when red blood cells stick together due to low air temperature (below 15 ° C) in the room.

In all these cases, either a repeated reaction is carried out, or using standard red blood cells.

Determination of Rh blood

To determine Rh status, i.e., to detect the presence or absence of Rh system antigens in people’s blood, standard anti-Rh sera (reagents) are used, varying in specificity, i.e., containing antibodies to various antigens of this system. To determine the Rh 0 (D) antigen, anti-Rhesus serum is most often used with the addition of a 10% gelatin solution, or a standard anti-Rhesus reagent prepared in advance with a 33% polyglucin solution is used. To obtain more accurate research results, as well as to identify antigens of other serological systems, the Coombs test is used (it is also very sensitive in determining the compatibility of transfused blood). For research, native blood or blood prepared with some preservative is used. In this case, the blood should be washed from the preservative with a tenfold volume isotonic solution sodium chloride. When determining Rh status- Rh 0 (D) two samples of serum or anti-Rhesus reagent of two different series should be used and at the same time standard red blood cells obtained from blood from Rh-positive (Rh +) and Rh-negative (Rh -) individuals should be used for control. When determining other isoantigens, control red blood cells that contain or lack the antigen against which the antibodies in the standard serum are directed should be used accordingly.

Partial heat agglutinins are the most common type of antibodies that can cause the development of autoimmune hemolytic anemia. These antibodies belong to IgG, rarely to IgM, IgA.

COOMBS TEST

Coombs test: introduction. The Coombs test is a laboratory diagnostic method based on the hemagglutination reaction.

The main method for diagnosing autoimmune hemolytic anemia is the Coombs test. It is based on the ability of antibodies specific to immunoglobulins (especially IgG) or complement components (especially S3) to agglutinate erythrocytes coated with IgG or S3.

The binding of IgG and C3b to erythrocytes is observed in autoimmune hemolytic anemia and drug-induced immune hemolytic anemia. Direct Coombs test. The direct Coombs test is used to detect antibodies or complement components fixed on the surface of red blood cells. It is carried out as follows:

To obtain antibodies to human immunoglobulins (antiglobulin serum) or complement (anticomplementary serum), the animal is immunized with human serum, immunoglobulins or human complement. The serum obtained from the animal is purified from antibodies to other proteins.

The patient's red blood cells are washed with saline to completely remove serum, which neutralizes antibodies to immunoglobulins and complement and can cause a false negative result.

If antibodies or complement components are fixed on the surface of red blood cells, the addition of antiglobulin or anti-complement serum causes agglutination of red blood cells.

The direct Coombs test is used in the following cases:

Autoimmune hemolysis.

Hemolytic disease of newborns.

Drug-induced immune hemolytic anemia.

Hemolytic transfusion reactions. Indirect Coombs test. The indirect Coombs test detects antibodies to red blood cells in serum. To do this, the patient's serum is incubated with group 0 donor red blood cells, and then a direct Coombs test is performed.

The indirect Coombs test is used in the following cases:

Determination of individual compatibility of donor and recipient blood.

Detection of alloantibodies, including antibodies that cause hemolytic transfusion reactions.

Determination of surface erythrocyte antigens in medical genetics and forensic medicine.

Confirmation of identical twins during bone marrow transplantation.

To conduct a biological test, blood begins to be transfused as quickly as possible (preferably in a stream). After transfusion of 25 ml of blood, the system tube is clamped with a clamp. Then there is a pause for 3 minutes, during which the recipient’s condition is monitored. To perform a biological test, 25 ml of blood is injected three times. At the end of the test (after transfusion of the first 75 ml of blood in fractional doses of 25 ml at intervals of 3 minutes), the system is adjusted to the required transfusion rate. When transfusing more than one bottle of blood to a patient, it is necessary to remove the needle from the vein. In this case, the needle is removed from the test tube of the vial in which the blood has run out and inserted into the next vial. The system tube (rubber or plastic) is clamped at this moment with a clamp. If during a blood transfusion it becomes necessary to administer any other drug intravenously to the recipient, this is done by piercing the rubber tube of the system. Punctures of the plastic tube are unacceptable, as they do not fall off. After each blood transfusion, the patient must be monitored to identify and promptly eliminate possible complications, including allergic reactions. 2 hours after the end of the blood transfusion, body temperature should be measured. If it increases, the measurement must be repeated every hour for the next 4 hours. Equally important is monitoring urination and urine composition, which makes it possible to establish the presence of a toxic post-transfusion reaction. The onset of oliguria and anuria after blood transfusion, the presence of blood cells and protein in the urine are a direct indication of the development of post-transfusion hemolysis.

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