Hemotransfusion: blood procurement, pretransfusion screening

More than 23 million units of blood components are transfused annually in the United States. Although transfusion procedures are now much safer than they once were, the risks (and public perception of risk) require informed patient consent for transfusion in all cases.

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Blood collection

In the United States, the collection, storage, and transportation of blood and its components is regulated by the Food and Drug Administration (FDA), the American Association of Blood Banks, and sometimes local health authorities. Donor selection includes 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 temporarily or permanently denied blood donation. The criteria for refusal are to protect the potential donor from possible negative consequences when donating blood, and the recipient from illness. Blood can be donated no more than once every 56 days. With rare exceptions, donors are not paid for donating blood.

Reasons for Delaying or Refusing to Donate Blood (USA)

Postponement

Refusal

Anemia. Use of certain medications. Execution Certain vaccinations. Malaria or risk of contracting malaria. Pregnancy. Transfusions within the last 12 months Recent contact with a patient with hepatitis. Recent tattoos. Uncontrolled hypertension

AIDS, high risk of infection (e.g. intravenous drug use, sexual contact with an HIV patient), male homosexuality. Use of bovine insulin since 1980 Cancer (except mild curable forms). Hereditary hemorrhagic diseases. Hepatitis. Military personnel who served at US military bases in the UK, Germany, Belgium, the Netherlands for 6 months between 1980 and 1990 or in Europe between 1980 and 1996. Recipients of any blood component in the UK from 1980 to present. Severe asthma. Severe heart disease. Residence in the UK (>3 months between 1980 and 1996), Europe (5 years since 1980) and France (>5 years since 1980)

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

Autologous blood donation, 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 red blood cell mass are collected with the patient prescribed iron preparations. Blood can also be collected using special techniques after injuries, surgeries for subsequent blood transfusions.

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Pretransfusion testing

Donor blood testing includes typing for ABO and Rh (D) antigens, antibody screening and testing for infectious disease markers.

Pre-transfusion compatibility testing includes testing the recipient's blood for ABO and Rh (D) antigens, screening the recipient's blood serum for antibodies to red blood cell antigens, and conducting a cross-compatibility test of the recipient's serum and donor red blood cells. Compatibility testing is performed immediately before transfusion; in emergency cases, testing is performed after blood is delivered from the blood bank. The data from these tests play a major role in diagnosing post-transfusion reactions.

Blood testing for transmissible infectious diseases

DNA detection	Determination of antigens	Determination of antibodies
Hepatitis C virus	Hepatitis B virus surface antigen	Hepatitis B virus core antigen
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 red blood cells. As a rule, the blood for transfusion should be the same as the recipient's ABO group. In urgent cases or when the ABO group is questionable or unknown, group O Rh-negative red blood cell mass, which 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 the Rh(D) factor (Rh negative) on red blood cells. Rh negative patients should always receive Rh negative blood, except in life-threatening situations when Rh negative blood is not available.

If antibodies are positive, this is confirmed by Western blot or recombinant immunoblot. Rh-positive patients may receive Rh-positive or Rh-negative blood. Sometimes, red blood cells from an Rh-positive person react weakly to standard Rh typing (weak D or D ^u positive), but these people are considered Rh-positive.

Antibody screening for rare anti-RBC antibodies is routinely performed in prospective recipients and prenatally on maternal blood samples. Rare anti-RBC antibodies are specific for red cell antigens other than A and B [e.g., Rh0(D), Kell (K), Duffy (Fy)]. Early detection is important because such antibodies can cause serious hemolytic transfusion reactions or hemolytic disease of the newborn and they can significantly complicate blood compatibility testing and the provision of compatible blood.

The indirect antiglobulin test (indirect Coombs test) is used to screen for rare anti-erythrocyte antibodies. These tests may be positive in the presence of rare anti-erythrocyte antibodies or when free (not bound to erythrocytes) antibodies are present in autoimmune hemolytic anemia. Control erythrocytes are mixed with the patient's serum, incubated, washed, tested with an antiglobulin reagent, and observed for agglutination. If antibodies are detected, their specificity is determined. Knowing 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 the newborn.

The direct antiglobulin test (direct Coombs test) measures antibodies that coat the patient's red blood cells in vivo. The test is used when immune hemolysis is suspected. The patient's red blood cells are directly tested with an antiglobulin reagent and agglutination is observed. A positive result, if consistent with clinical data, suggests autoimmune hemolytic anemia, drug-induced hemolysis, transfusion reaction, or hemolytic disease of the newborn.

Determination of the antibody titer is performed if it is clinically important in the detection of rare anti-erythrocyte antibodies in the serum of pregnant women or in patients with cold autoimmune hemolytic anemia. The maternal antibody titer correlates significantly with the severity of hemolytic disease in a fetus with incompatible blood group. Its determination is often used as a guideline in the treatment of hemolytic disease of the newborn in conjunction with ultrasound examination and amniotic fluid examination.

Additional cross-matching, ABO/Rh typing, and antibody screening improve the accuracy of incompatibility determination by only 0.01%. If the recipient has clinically significant anti-RBC antibodies, donor blood is limited to selection of RBCs negative for the corresponding antigens. Further compatibility testing is performed by combining recipient serum, donor RBCs, and antiglobulin reagent. In recipients without clinically significant anti-RBC antibodies, direct cross-matching, without performing the antiglobulin phase, confirms ABO compatibility.

Urgent transfusion is performed when there is insufficient time (less than 60 min) to perform all tests completely, when the patient is in hemorrhagic shock. If time permits (approximately 10 minutes), an ABO/Rh compatibility test is performed. In more urgent circumstances, if the blood group is unknown, type O is transfused, and if the Rh type is uncertain, Rh-negative blood is transfused.

A full blood test may not be required in all cases. The patient's blood is typed for ABO/Rh antigens and screened for antibodies. If no antibodies are detected, then in cases where transfusion is necessary, ABO/Rh compatibility testing without the antiglobulin phase of the cross-reaction is sufficient. In the presence of rare antibodies, a full blood test for compatibility is required.