1. Pretranfusion Compatibility Testing
Mr. Mohammed A. Jaber

2. Blood Transfusion Process
Pre-transfusion
Transfusion
Post-transfusion

3. What is compatibility testing?
Also called pretransfusion testing
Purpose:
To select blood components that will not cause harm to the recipient and will have acceptable survival when transfused
If properly performed, compatibility tests will confirm ABO compatibility between the component and the recipient and will detect the most clinically significant unexpected antibodies

4. Compatibility testing?
There are several components of compatibility testing
Proper specimen collection
Reviewing patient transfusion history
ABO, Rh, and antibody testing (screen/ID)
Crossmatching
Actual transfusion

5. Compatibility testing
Can be divided into 3 categories:
Preanalytical procedures
Serological testing
Postanalytical procedures

6. Pre-analytical phases
Patient identification
Specimen collection
Review of patient history

7. Patient Identification
Must confirm recipient’s ID from bracelet ON the patient
Full patient name and hospital number
Name of physician

8. Sample Identification
The sample should also have the full patient name, hospital number, and physician
Date and time of collection, phlebotomist’s initials
All of this should be on the request form and the sample

9. Specimen Tubes
Pink Top - EDTA
Red Top – no additives

10. Specimen Collection Collected in tube with EDTA or no additives
If the venipuncture causes hemolysis, the sample may be rejected
True hemolysis in the patient is the result of complement activation
Samples are labeled at the bedside (pre-labeling is not recommended)
A record of individuals who collect (or test) the specimens should be documented in order to “backtrack” in case of an error

11. Specimen Collection
If the sample is drawn from an IV line, the IV infusion should be stopped 5-10 minutes prior to blood drawing and the first 10 mL discarded
Testing should be performed on samples less than 72 hours or else complement dependent antibodies may be missed (complement can become unstable)

12. Getting the history
Look at recipient’s records for any prior unexpected antibodies
Previous transfusion reactions

13. Serological Testing 3 tests: ABO/Rh Antibody detection/identification
Crossmatch

14. ABO/Rh Typing In the ABO typing, the forward and reverse MUST match
In the Rh typing, the control must be negative
Both of these will indicate what type of blood should be given

15. Antibody screen and/or ID
The antibody screen will detect the presence of any unexpected antibodies in patient serum
If antibodies are detected, identification should be performed using panel cells (with an autocontrol) IS
37° (LISS)
AHG
If an antibody is present, units negative for the antigen must be given
Proceed to the crossmatch…

16. Crossmatching Purpose: Prevent transfusion reactions
Increase in vivo survival of red cells
Double checks for ABO errors
Another method of detecting antibodies

17. Crossmatch Two types of crossmatches
Major – routinely performed in labs
Minor – not required by AABB since 1976

18. Major vs Minor Crossmatch
Why is the minor crossmatch unnecessary?
Donated units are tested for antibodies
Most blood is transfused as packed cells, having little antibodies
The plasma volume is small, and Abs will be diluted in recipient circulation
Major: Patient serum crossmatched with donor red cells.
Minor: Donor serum crossmatched with patient red cells. Antibody screen testing on donor samples has replaced the minor crossmatch.

19. Crossmatches
The crossmatch “shall use methods that demonstrate ABO incompatibility and clinically significant antibodies to red cell antigens and shall include an antiglobulin phase”

20. Crossmatch No agglutination ~ compatible Agglutination ~ incompatible
Donor RBCs (washed)
Patient serum

21. The procedure
Donor cells are taken from segments that are attached to the unit itself
Segments are a sampling of the blood and eliminate having to open the actual unit

22. Units of whole blood with segments attached

23. Procedure ABO/Rh typing is FIRST performed
Antibody Screen is performed next….

24. Crossmatch Procedure if antibodies are NOT detected:
Only immediate spin (IS) is performed using patient serum and donor blood suspension
This fulfills the AABB standard for ABO incompatibility
This is an INCOMPLETE CROSSMATCH
If antibodies ARE detected:
Antigen negative units found and X-matched
All phases are tested: IS, 37°, AHG
This is a COMPLETE CROSSMATCH

25. The type and screen consists of ABO/Rh, antibody screen, and a  records check.
This procedure is used most frequently to screen pre-operative or obstetrical patients whose risk of excessive blood loss is minimal. In case of an emergency, where blood is needed for these patients, uncrossmatched ABO and D compatible blood can be released with 99.9% assurance of safety, as long as the patient has no unexpected antibodies.
If the antibody screen is positive the patient is not a T&S candidate, the antibody present in the serum or plasma must be identified and antigen negative donor units must be crossmatched.

26. Crossmatches… Will Will Not Verify donor cell ABO compatibility
Detect most antibodies against donor cells
Will Not
Guarantee normal survival of RBCs
Prevent patient from developing an antibody
Detect all antibodies
Prevent delayed transfusion reactions
Detect ABO/Rh errors

27. Incompatible crossmatches
Antibody screen
Crossmatch
Cause
Resolution
Pos
Neg
Antibody directed against antigen on screening cell
ID antibody, select antigen negative blood
Antibody directed against antigen on donor cell which may not be on screening cell OR donor unit may have IgG previously attached
ID antibody, select antigen negative blood OR perform DAT on donor unit
Antibodies directed against both screening and donor cells
Antibody ID, select antigen negative blood

28. Additional Information on Types of Compatibility Tests
Manual (IS and IAT)
Gel Technology
Electronic (Computerized) Cross match
Red cell Affinity Column Technology (ReACT)
Solid Phase Adherence Assays (SPAA)

29. Manual (IS and IAT)
Antibody
Acquired
Naturally occuring
(Cold agglutinin)
Alloantibody
Autoantibody
IS: Immediate Saline
IS detect RT reactive antibodies (Auto, Alloantibody, Naturally occuring)
IAT detect IgG antibodies (Auto & alloantibody)

30. Gel Technology
Patient serum, and 1% of suspended RBCs in LIM are dispensed into the microtube and incubated at 37oC for 15 minutes.
The card containing the microtubes is then centrifuged at a controlled speed for 10 minutes.
At the start of centrifugation the cells are separated from the serum; then they meet the AHG contained in the microtube.
Finally the cells are trapped by the gel (if agglutinated) or pellet to the bottom of the tube.
Low ionic media

31. New Technologies… The electronic crossmatch
According to the AABB, the following must be fulfilled:
Critical elements of the information system have been validated on-site.
No clinically significant antibodies are detected in the current blood sample and there is no record of clinically significant antibodies in the past

32. Computer crossmatch (cont’d)
The patient's ABO group and Rh type has been done twice and entered in the computer
The donor ABO/Rh have been confirmed and entered in the computer. The donor unit identification number, component name, and ABO/Rh type must also be entered in the computer
The computer system will alert the technologist to ABO & Rh discrepancies between information on the donor label and results of donor confirmatory testing

33. Red Cell Affinity Column Technology (ReACT)
Based on affinity adherence of coated red cells in an immunologically active matrix.
Antibody- sensitized red cells bind or adsorbed to ligands attached to an agarose matrix.
The main ligand is Protein G (prepared from Group C or G Streptococcus or by recombinant technology), which has high affinity for all four IgG subclasses.
Another ReACT ligand is Protein A (from Group A Staphlococcus), which binds to IgG 1, 2, and 4.

34. Red Cell Affinity Column Technology (ReACT)
Positive reaction: the coated red blood cells with IgG are boud to immunoreactive gel particles, occurs mostly at the top of the gel column.
Negative reaction: the red blood cells are not coated with antibody and pass through to the bottom of the gel column.

35. Solid Phase Adherence Assays (SPAA)
Uses red cell membrane bound to the surfaces of polystyrene microtitration strip wells, capturing IgG antibodies (if present) in patient sera.
Patient serum is added to wells coated with screen cells
Incubated at 37oC for 15 min.
Washing
anti-IgG-coated indicator red cells are added.
centrifuge

36. indicator cells forming distinct ring
SPAA
Result:
Positive
Negative
dispersed cells
indicator cells forming distinct ring

37. Post-analytical phase
Involves labeling, inspecting, and issuing the blood unit
Labeling form includes patient’s full name, ID number, Location, ABO/Rh(D) of patient and unit, donor #, compatibility results, and tech ID
Form is attached to the donor unit and only released for the recipient
The unit is visually inspected for abnormalities, such as bacterial contamination, clots, etc

38. Issuing blood
When it’s time to release a blood product to the nurse or physician, a few “checks” must be done
Requisition form
Comparing requisition form  donor unit tag  blood product label
Name of persons issuing and picking up blood
Date and time of release
Expiration date

39. What if the unit is unused?
Blood can be returned to the blood bank if it is not needed for transfusion
Unit closure has to remain unopened
Storage temperature must have remained in the required range (1° to 10°C for RBCs)
If not at correct temp, unit must be returned within 30 minutes of issue

40. Special Circumstances

41. Emergency Release
In an emergency, there may not be enough time to test the recipient’s sample
In this case, blood is released only when signed by the physician (O negative)
The tag must indicate it is not crossmatched
Segments from the released units should be retained for X-matching
Every detail is documented (names, dates..)

42. Emergency Release
Once the specimen is received, ABO/Rh typing and antibody screening should be performed
Crossmatching the segments from the released unit should be tested
In addition, the lab may crossmatch additional units as a precaution if more blood is needed
If death should occur, testing should be complete enough to show that the death was unrelated to an incompatibility

43. What can be given in an emergency?
Group O Rh(D)-negative red cells or AB plasma
Emergency release
Women below or of childbearing age
Group O Rh(D)-positive red cells
Used as a substitution if O negative is not available
Male or elderly females

44. Massive transfusion
Defined as a transfusion approaching or exceeding the recipient’s own blood volume (about 5 liters or units in an adult male) within 24 hour period
The original sample no longer represents the patient’s condition
Complete crossmatch not necessary (if no antibodies were detected originally)
Give ABO identical units
If antibodies were originally ID’s, continue to give antigen negative units

45. Donor Selection: Appropriate donor units to give
ABO specific blood should always be given first.
When ABO-specific blood is not available or is in less than adequate supply, alternative blood groups are chosen as summarized in the following table; (must be administered as red blood cells).
Patient’s Type
1st Choice
Other Choices O
None A B AB
A, O, B only one of the three should be used for a given patient
Note that for AB individuals the Second Choice lists group O as the next logical choice. Group B blood is relatively uncommon, you would not wish to deprive group B patients of type specific blood, so it makes more sense to choose group O, which is usually in abundant supply.
For plasma components group O is the universal recipient, since they have all ABO antibodies present all plasma products will be compatible. Group AB is the universal donor for plasma products since they lack all ABO antibodies.

46. Selection of Appropriate Donor Units.
Rh-negative blood can be given to Rh-positive patients, however, good inventory management should conserve this limited resource for use in Rh-neg recipients.
If Rh-neg units is near expiration, the unit should be given rather than wasted.

47. Selection of Appropriate Donor Units.
Rh-pos blood should not be given to Rh(D) -neg women of childbearing age.
Transfusion of Rh-neg male patients and female patients beyond menopause with Rh-pos blood is acceptable as long as no performed anti-D is demonstrable in the sera.

48. Major Crossmatch Tests
It is done both for IgM and IgG antibodies
Requirement:
1. Recipient’s serum.
2. Donor’s red cells taken from the tube attached to the bag.
Saline technique
Saline technique is designed to detect compatibility of IgM antibody(ies) in patient’s serum against antigens on donor’s red cells.

49. Method Label 1 tube for each donor sample to be tested.
Put 2 drop of patient’s serum in labeled tube.
Add 1 drop of 2-5% saline suspended red cells of donor
Mix and incubate for 5-10 min. (spin method) or incubate for min (sedimentation method) at RT.
Centrifuge at 1000 rpm for 1 min. in spin method (after 5-10 min. incubation);centrifugation is optional in sedimentation method.

50. Read the result, observe for hemolysis and agglulination.
Negative result should be confirmed under microscope.
Interpretation
Agglutination or hemolysis indicates a positive result (incompatible)
Note: In emergency spin technique is acceptable.
Saline technique is inadequate as a complete compatibility test because it is inadequate to detect clinically significant IgG antibodies.

51. Crossmatch Test for IgG Antibody(ies)
Anti -Human Globulin Test (IAT)
Indirect anti human globulin test (IAT) is the most important and widely used serological procedure
in modern blood banking to test the IgG compatibility between recipient’s serum and donor’s cells. The majority of incomplete antibodies are IgG and are detected by AHG test.

52. Method Put 2 drops of patient’s serum in a labeled tube.
Add 1 drop of 2-5 % saline suspended red cells of donor.
Incubate for min at 37° C
Centrifuge at 1000 rpm for 1 min, check for hemolysis/agglutination
If there is no hemolysis/agglutination, wash the cells three times with normal saline.

53. Add IgG coated red cells to negative AHG test.
Perform IAT test
Add 2 drops of polyspecific AHG serum to washed cells
Centrifuge at 1000 rpm for 1 minute
See for agglutination
Add IgG coated red cells to negative AHG test.
Centrifuge and check for agglutination - if there is no agglutination test is invalid.

54. Interpretation
Hemeolysis or agglutination at any stage indicates incompatibility.
Note: Cross-match can be done by two tubes technique for IgM and IgG separately as described above or by one tubes in which donor’ cell and the patient’s serum after step 5 in saline technique is incubated at 37°C for minutes and then do IAT.
In major-cross for IgG antibodies albumin or enzyme or LISS can be used with IAT to increase sensitivity. For techniques see chapter on Antiglobulin Test.