Blood transfusion: pre-transfusion examination

More than 23 million doses of blood components per year are poured into the United States. Despite the fact that at present the procedure of blood transfusion is much safer than before, the risk (and public perception of risk) requires the patient's informed consent to blood transfusion in all cases.

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Blood collection

In the US, the procurement, storage and transportation of blood and its components is regulated by the FDA (Food and Drug Administration), the American Blood Bank Association and sometimes by local health authorities. Donor selection involves filling out a detailed questionnaire, talking to a doctor, measuring body temperature, heart rate, blood pressure and determining hemoglobin levels. In some cases, potential donors are denied blood surrender temporarily or permanently. The refusal criteria are protection of the potential donor from possible negative consequences when donating blood, and the recipient from the disease. The delivery of blood can be performed no more than 1 time every 56 days. With rare exceptions, blood donors are not paid for.

The reasons for delay or denial of blood (USA) 

Postponement

Renouncement

Anemia. The use of certain medications. Performance Specific vaccinations. Malaria or the risk of contracting malaria. Pregnancy. Transfusion in the last 12 months Recent contacts with a patient with hepatitis. Recent tattoos. Uncontrolled hypertension

AIDS, a high risk of infection (eg, intravenous drug use, sexual contact with a patient with HIV), male homosexuality. The use of bovine insulin since 1980. Cancer (except for easy curable forms). Hereditary hemorrhagic diseases. Hepatitis. Servicemen who served on US military bases in Great Britain, Germany, Belgium, the Netherlands 6 months between 1980 and 1990. Or in Europe between 1980 and 1996. Recipients of any blood component in the UK from 1980 to the present. Severe asthma. Severe heart disease. Stay in the UK (> 3 months between 1980 and 1996), Europe (5 years since 1980) and France (> 5 years since 1980)

The standard volume for delivery of blood is 450 ml of whole blood, which is collected in a plastic bag containing an anticoagulant. Whole blood or erythrocyte mass with a preservative containing citrate-phosphate-dextrose-adenine can be stored for up to 35 days. Erythrocyte mass with the addition of a preservative containing adenine-dextrose-sodium chloride can be stored for up to 42 days.

Autologous blood lead, in which the patient is transfused with his own blood, is the safest method of transfusion. 2-3 weeks before surgery, 3-4 doses of whole blood or erythrocyte mass are collected with the appointment of iron preparations to the patient. Blood can also be collected with the help of special techniques after trauma, surgical operations for subsequent blood transfusions.

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Pre-transfusion examination

The study of donor blood includes typing on ABO and Rh (D) antigens, screening for antibodies and screening for markers of infectious diseases.

The compatibility test before transfusion involves determining the recipient's blood on ABO and Rh (D) antigens, screening the recipient's serum for antibodies to red cell antigens; the reaction of cross-matching of the recipient's serum and donor's erythrocytes. Compatibility studies are performed just prior to transfusion, in emergency cases, testing is performed after blood delivery from the blood bank. The data of the conducted examinations play an important role in the diagnosis of posttransfusion reactions.

Testing of blood for vector-borne infectious diseases 

Determination of DNA	Definition of antigens	Definition of antibodies
Hepatitis C virus	The surface antigen of the hepatitis B virus	Core antigen of the hepatitis B virus
HIV	HIV-1 p24	Hepatitis C
West Nile Virus	Syphilis	HIV-1 and-2. Human T-cell lymphotropic virus I and III

ABO typing of donor and recipient blood is performed to prevent transfusion incompatibility of erythrocytes. Typically, blood for transfusion should be in the ABO group the same as that of the recipient. In urgent cases or when the ABO group is doubtful or unknown, the erythrocyte mass of the O-Rh-negative group that does not contain A- and B-antigens can be used for patients with any blood group.

Rh-typing determines the presence (Rh-positive) or absence of Rh (D) factor (Rh-negative) on red blood cells. Rh-negative patients should always receive Rh-negative blood, except in situations that threaten life, when Rh-negative blood is not available.

When positive antibodies are confirmed using Western blot or recombinant immunoblotting. Rh-positive patients can receive Rh-positive or Rh-negative blood. Sometimes red blood cells from the Rh-positive person respond poorly to standard Rh-typing (weak D or D ^u positive), but these people are considered Rh-positive.

Antibody screening for rare anti-erythrocyte antibodies is routinely performed in suspected recipients and prenatally on maternal blood samples. Rare anti-erythrocyte antibodies are specific for erythrocyte antigens other than A and B [for example, Rh0 (D), Kell (K), Duffy (Fy)]. Early detection is important, since such antibodies can cause severe hemolytic transfusion reactions or a hemolytic disease of the newborn and, in addition, they can significantly complicate the testing of blood for compatibility and the provision of compatible blood.

An indirect antiglobulin test (indirect Coombs test) is used to screen for rare anti-erythrocyte antibodies. These tests can be positive in the presence of rare anti-erythrocyte antibodies or when free (non-red blood cells) antibodies are present in autoimmune hemolytic anemia. The control erythrocytes are mixed with the patient's serum, incubated, washed, tested with an antiglobulin reagent and observed for agglutination. When detecting antibodies, their specificity is determined. Knowledge of the specificity of antibodies helps to assess their clinical significance, which is important for the selection of compatible blood and the management of hemolytic disease of newborns.

A direct antiglobulin test (Coombs direct test) identifies antibodies that cover the patient's erythrocytes in vivo. The test is used for suspected immune hemolysis. Erythrocytes of the patient are directly tested with an antiglobulin reagent and observed for agglutination. If the result is positive, if there is compliance with the clinical data, autoimmune hemolytic anemia, drug-induced hemolysis, transfusion reaction or hemolytic disease of the newborns is suspected.

Determination of the antibody titer is performed if it is clinically important for the establishment of rare anti-erythrocyte antibodies in the serum of pregnant women or in patients with cold autoimmune hemolytic anemia. The titer of the antibodies of the mother largely correlates with the severity of hemolytic disease in the incompatible fetal group. Its definition is often used as a guide in the treatment of hemolytic disease of newborns together with ultrasound examination and study of the amniotic fluid.

An additional study of cross-compatibility, ABO / Rh-typing and antibody screening increases the accuracy of incompatibility detection by only 0.01%. If the recipient has clinically significant anti-erythrocyte antibodies, the donor blood is limited to the selection of erythrocytes, negative for the corresponding antigens. Further compatibility testing is performed by combining the serum of the recipient, the donor's erythrocytes and the antiglobulin reagent. In recipients without clinically significant anti-erythrocyte antibodies, a direct study of cross-compatibility, without performing an antiglobulin phase, confirms compatibility in the ABO system.

Urgent transfusion is performed in the absence of sufficient time (less than 60 minutes) to fully perform all tests when the patient is in hemorrhagic shock. If time allows (it takes about 10 minutes), the ABO / Rh compatibility test is performed. In more urgent circumstances, with an unknown blood group, the O group is transfused and, for an undefined Rh type, Rh-negative blood.

A complete blood test may not be required in all cases. The patient's blood is typed on ABO / Rh antigens and screened for antibody content. If the absence of antibodies is detected, then, in cases of transfusion, it is sufficient to determine the compatibility of ABO / Rh without the cross-reacting antiglobulin phase. In the presence of rare antibodies, it is necessary to perform a full blood test for compatibility.