Pretransfusion testing

pretransfusion testing

1. Pretransfusion Testing

2. Introduction Pretransfusion testing can be defined as the use of serologic principles and tests to ensure compatibility and prevent an immune-mediated hemolytic transfusion reaction. Pretransfusion activities,including proper specimen collection, pretransfusion and compatibility tests, special clinical situations, and patient safety

3. Specimen Collection Facilities must strictly follow policies and procedures to identify patients and collect properly labeled specimens to mitigate misidentification errors and improve patient safety. Positive Patient Identification and Specimen Labeling
Specimen Requirements

4. 1.Positive Patient Identification and Specimen Labeling If the patient is conscious at the time of taking the sample, ask him or her to identify themselves by given name, bed number. If the patient is unconscious, ask the relative or second member of the staff to verify the patient’s identity. Send the completely filled blood requisition form along with properly labelled 5 ml blood sample in plain test tube/EDTA.

5. 2. Specimen Requirements Either anticoagulated or clotted specimens are acceptable for pretransfusion testing. Anticoagulated specimens are often preferred due to ease of handling. Red blood cells from an anticoagulated sample are ideal for preparing a uniform cell suspension for testing. Clotted red blood cells may require additional washing steps to minimize interference in test interpretations. In addition, serum may contain small fibrin clots that can be difficult to distinguish from true agglutination. Anticoagulated specimens can inactivate complement binding antibodies due to calcium chelation disrupting the complement cascade.

6. Intravenous line (iv) contamination is unacceptable, and the use of hemolyzed samples should be avoided. IV contam inants from the infusion fluid dilute otherwise detectable antibodies in the specimen and may produce erroneous results. specimens should be collected from the arm opposite the iv catheter and never above it. If venous access is limited and the specimen must be collected from the iv line, the infusion fluid must be stopped and the line flushed. It is recommended that an amount of blood equal to three or more times the dead space of the catheter be discarded The use of hemolyzed specimens can mask antigen-antibody–mediated hemolysis and create difficulties in evaluating test results. If a new specimen cannot be obtained, results must be interpreted carefully.

7. The age of the specimen used in pretransfusion testing is crucial. If a patient has been transfused or pregnant within the past 3 months or if the patient’s history is unknown, a specimen must be collected every 3 days for antibody screen ing and compatibility testing. The date of the collection is considered day 0, and the specimen expires at midnight on day 3. The 3-day testing window minimizes the risk of an adverse reaction due to an emerging alloantibody in a recipient that has been recently transfused. However, the transfusion and pregnancy histories must be known with certainty and neither can have occurred in the previous 3 months.

8. Pretransfusion specimens and donor unit segments are typically stored at 2° to 8°c and must be retained in the event that additional testing is warranted. The patient sample and a segment from the donor unit must be retained post-transfusion for at least 7 days. This allows for the investigation of any adverse events related to transfusion, such as a delayed hemolytic transfusion reaction.

9. Compatibility Tests Compatibility tests are performed to prevent an immunemediated hemolytic transfusion reaction. Compatibility tests include: determining the recipient’s ABO group and Rh type, screening for any unexpected antibodies, and crossmatching the donor unit with the recipient’s plasma. Review of Records- Current results such as ABO group and Rh type, detection of clinically significant antibodies, significant adverse events, and special transfusion requirements must be compared to historical records. Recipient Testing- ABO grouping, Rh typing, and screening for unexpected antibodies must be performed within 3 days prior to the scheduled transfusion.

10. ABO Grouping : The ABO blood group continues to be the most important blood group in transfusion and transplantation due to immunogencity . Can be performed using tubes, column-agglutination technology, or in microtiter plates used in solid-phase red cell adherence tests. All ABO discrepancies must be resolved in order to transfuse appropriately. If an ABO discrepancy cannot be resolved prior to the need for transfusion, group O red blood cells should be selected.

11. Rh Typing : Rh typing is performed to detect the presence or absence of the D antigen. IgM promotes direct agglutination of red blood cells at room temperature, whereas IgG is utilized in the indirect antiglobulin test (IAT) for the detection of the weak D antigen. Rh control must be tested in parallel with anti-D reagent in the indirect antiglobulin test for weak D determination. If the Rh control is positive at any phase of testing, the tests results are invalid and additional testing is required. Rh-negative recipients should receive Rh-negative red blood cells to prevent the production of anti-D alloantibodies.

12. Antibody Screening : Antibodies to blood group antigens must be detected and their clinical significance assessed. Clinically significant antibodies have been associated with red blood cell destruction, hemolytic transfusion reactions, and hemolytic disease of the fetus and newborn (HDFN). The FDA mandates that red blood cells used in antibody detection tests must express the following antigens: D, C, E, c, e, K, k, Fya , Fyb , Jka , Jkb , Lea, Leb , P1, M, N, S, and s. Low-incidence antigens such as V, Cw , Kpa , or Jsa are not required because they rarely cause development of the corresponding antibody.

13. Selection of Donor Units A common goal shared by blood suppliers and transfusion services is to provide a safe and efficacious blood component that benefits the intended recipient. Donor Unit Testing :- Blood suppliers are required to perform a battery of tests on blood components prior to distribution. ABO grouping, Rh typing, a weak D test if the initial Rh typing result is negative, and a screen for antibodies to common blood group antigens. Required infectious disease testing on donor units includes HBV DNA, HBsAG , HBc antibodies, HCV antibodies, HCV RNA, HIV1/2 antibodies, HIV-1 RNA, HTLV I/II antibodies, WNV RNA, and a serologic test for syphilis. Atleast once for antibodies to Trypanosoma cruzi . Recently, the FDA provided guidance and recommended universal testing for the Zika virus.

14. Selection Criteria :- ABO antigens on the donor unit red blood cells must be compatible with the naturally occurring anti-A and/or anti-B in the recipient’s plasma. If whole blood is the only option, the product and the recipient must be ABO identical due to the plasma portion of the blood component. Rh-negative red blood cells may be given to Rh-positive recipients. If a patient has a history of, or has detectable clinically significant antibodies, donor units selected for transfusion must be negative for the corresponding antigen(s).

15. Platelets, Thawed Plasma, and Cryoprecipitate :- No compatibility testing is required for the transfusion of platelets, thawed plasma, and cryoprecipitate. Either a current or a historical ABO grouping is sufficient. Rh typing is ignored because these components contain very few red blood cells as a result of collection methods or frozen storage. ABO-identical platelet units should be selected whenever possible to ensure adequate platelet survival. Plasma units should be compatible with the recipient’s ABO red blood cell antigens.

16. Crossmatch Tests A serologic crossmatch consists of mixing recipient plasma with cells directly obtained from the donor unit to detect ABO or blood group antibody incompatibilities. A nonreactive serologic crossmatch indicates the donor unit is compatible and safe for transfusion. Immediate Spin Crossmatch :- If no clinically significant antibodies are detected and there is no history of antibody, a serologic test to detect ABO incompatibility is sufficient. Recipient plasma is mixed with cells from the donor unit, immediately centrifuged, and observed for agglutination and/or hemolysis. Absence of either indicates ABO compatibility, whereas positive results require further investigation.

17. Possible reasons for incompatibilities and subsequent resolutions include the following: Incorrect ABO grouping of recipient or of donor unit selected 2. Cold-reactive allo - or autoantibody in the plasma not detected in antibody detection tests. 3. Abnormalities in the recipient’s plasma Antiglobulin Crossmatch Once a clinically significant antibody has been detected, an antiglobulin crossmatch is required. The donor unit selected should be antigen-negative for the corresponding alloantibody identified. The antiglobulin crossmatch consists of an immediate spin crossmatch with the recipient’s plasma and cells from the donor unit. The test system is then incubated at 37°C and completed with the antiglobulin test. Observable reactivity and/or hemolysis at any phase of testing indicate incompatibility. Subsequent testing should include an anti -globulin testing phase and the addition of an autocontrol .

18. Possible reasons for incompatibilities include the following: 1. New alloantibody is present in recipient’s plasma. 2. Alloantibody to a low-incidence present is on the donor unit red blood cells. 3. Warm-reactive autoantibody is present in the recipient’s plasma. 4. Donor unit has a positive direct antiglobulin test (DAT).

19. Special Circumstances Emergent Transfusions :- Prior to the completion of pretransfusion testing, urgent situations may arise when it is medically necessary to transfuse blood components. If the blood type of the recipient is unknown, group O red blood cells are required. ABO group-specific red blood cells may be issued once a blood type is obtained.

20. Massive Transfusions:- Massive transfusion is defined as the administration of 8 to 10 red blood cell units to an adult patient in less than 24 hours or acute administration of 4 to 5 units within 1 hour. The American College of Surgeons recommends transfusion of red blood cells, thawed plasma, and platelets in a ratio of 1:1:1 for effective blood component resuscitation. Goal of treatment is to restore blood volume rapidly to a level adequate to maintain hemostasis, oxygen-carrying capacity, oncotic pressure, and biochemical parameters.

21. Neonatal Transfusions:- Pretransfusion testing may be abbreviated in infants less than 4 months of age. Either the infant’s or mother’s plasma may be used for antibody screening and any necessary compatibility testing. If a clinically significant antibody is identified, the donor unit selected must be either antigen-negative for the corresponding antibody or antiglobulin crossmatch compatible until the antibody is no longer demonstrable in the infant’s plasma. If an infant has a negative antibody screen and will only receive group O red blood cell transfusions.

22. Intrauterine Transfusions:- Intrauterine transfusions (IUT) are indicated in severe cases of fetal anemia . Intrauterine transfusions are performed by inserting a needle into the umbilical vein using high-resolution sonography to guide the procedure. Fetal samples may be obtained for testing to include blood typing, direct anti - globulin test, antigen typing, and bilirubin levels. The fetal blood type is unknown, and group O Rh-negative red blood cells should be selected. The unit should be fresh (<7 days old), leukocyte-reduced, irradiated to prevent transfusion- associated graft-versus-host disease, and negative for hemoglobin associated with sickling. In cases in which maternal antibody is present, the unit should be antigen-negative and crossmatch compatible at the antiglobulin phase of testing.

23. Issuance of Blood Components Donor units must be labeled appropriately at the time of issue. All special transfusion requirements must be met and the unit visually inspected for any abnormalities such as hemolysis or the presence of clots. Blood components must not be issued until all discrepancies have been resolved. The transfusionist is responsible for confirming the intended recipient’s identification and the donor unit information at the bedside. Blood components are administered according to the facility’s policy, with any adverse event related to the transfusion investigated.

24. Conclusion The transfusion service partners with almost all clinical areas to ensure safe transfusions. This partnership is responsible for all aspects of transfusion, including specimen collection, pretransfusion and compatibility testing, blood administration, and the investigation of any adverse event.

25. SUMMARY Clerical error and ABO incompatibility are implicated in fatal transfusion reactions. Pretransfusion specimens, labels, and testing requests must contain two unique identifiers. Specimen draw date and time and the collecting individual must be traceable back to the collection of the patient sample. Pretransfusion specimens must be collected within 3 days of the scheduled transfusion. Review of records prior to transfusion is essential for safety. Selection of donor unit is based on ABO grouping, Rh typing, current and historical antibody screening results, and any special requirements. Perform immediate spin, antiglobulin, or computer crossmatch based on current or historical serologic results.

26. Platelets, thawed plasma, and cryoprecipitate transfusions require a historical or current ABO grouping only. No compatibility testing required. Emergency transfusions: Select uncrossmatched, group O, Rh-negative or Rh-positive red blood cell units based upon patient’s sex and age. Massive transfusions: The American College of Surgeons recommends transfusion of red blood cells, thawed plasma, and platelets in a ratio of 1:1:1. Neonatal transfusions: • Select a group O, Rh-compatible red blood cell unit. • Perform an antibody screen and any required compatibility testing with either an infant’s or mother’s specimen. Intrauterine transfusion: • Select a group O, Rh-negative red blood cell unit that is fresh, leukocyte-reduced, irradiated, negative for sickling hemoglobin, and antigen-negative, if applicable.

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