2. drmsaiem
COMPATIBILITY TESTING
The cross-match became part of a series of pre-
transfusion test known as compatibility testing. The
compatibility test includes an ABO and Rh grouping
performed on the donor and recipient samples, screening
of the donor’s and patient’s sera for unexpected
antibodies, and a cross-match.
The purpose of pre-transfusion or compatibility testing is
to ensure the best possible results of a blood transfusion.
The transfused red cells will have an acceptable survival
rate, and there will be no significant destruction of the
recipient’s own red cells.
3. drmsaiem
COMPATIBILITY TESTING
Collection and Preparation of Samples.
Positive Patient Identification
The major cause of transfusion associated fatalities have
been clerical errors resulting in incorrect ABO grouping
The most common cause of clerical errors and thus
transfusion accidents is misidentification of the
patient involved in the transfusion. Confusion in
identification of the patient when the blood sample was
drawn a mixed up samples during handling in the lab,
and error in identification of the patient when the
transfusion was given.
4. drmsaiem
COMPATIBILITY TESTING
To prevent collection of samples from the wrong patient,
the blood request form must be used to confirm the
patient’s identity before phlebotomy is performed. The
request form must state the intended recipient’s full
name, and unique hospital identification number.
Other information such as age and date of birth, address,
sex, and name of requesting physician can be used to
verify patient identity further but is not required on the
form.
5. drmsaiem
COMPATIBILITY TESTING
Collecting Patient Samples
Hemolyzed samples can not be used for testing
because hemolysis caused by activation of complement
Serum or plasma may be used for pre-transfusion testing.
Most blood bank technologist prefer serum because plasma
may cause small fibrin clots to form which may difficult to
distinguish from true agglutination.
6. drmsaiem
COMPATIBILITY TESTING
When a specimen is received in the lab, a blood bank
technologist must confirm that the information on the
sample and requisition form agree.
All discrepancies must be resolved before the sample is
accepted, and if any doubt exists, a new sample must be
drawn.
7. drmsaiem
COMPATIBILITY TESTING
Donor Samples.
Donor testing samples must be taken when the full donor
unit is drawn. Depending on the method used for testing,
clotted sample, anti-coagulated samples, or both, are
obtained.
Donor information and medical history card, the pilot
samples for processing, and the collection bag must all
be labeled with the same unique number code before
starting the phlebotomy, and the numbers must be
verified again immediately after filling.
8. drmsaiem
Compatibility Testing Protocols.
Selection of Appropriate Donor Units.
In almost all cases, blood and blood components of the
patient’s own ABO and Rh group should be selected for
transfusion.
When blood and blood components of the patient’s type
are unavailable or when some other reason precludes
their use, units selected must lack any Ag against which
the patient has a significant Ab.
9. drmsaiem
Selection of Appropriate Donor Units.
When transfusion of an ABO group different from the
recipient must be given, packed red cells must be used
rather than whole blood which contains plasma Abs that
are incompatible with the patient’s red blood cells.
Group O packed red blood cells can be safely used for all
patients, however, conservation of a limited supply of
group O blood should dictate its use for patients of other
AB types only in special circumstances.
10. drmsaiem
Selection of Appropriate Donor Units.
If ABO-specific blood is not available or is in less than adequate
supply, alternative blood groups are chosen as summarized in the
following table;
Patient ‘s BG Alternative BG given as packed cells
O NONE
A O
B O
AB A, B, O
only one of the three should be used for a given patient
11. drmsaiem
Selection of Appropriate Donor Units.
Rh-negative blood can be given to Rh-positive patients,
however, good inventory management again 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.
12. drmsaiem
Testing of the donor sample
The transfusing facility is required by AABB standards to
confirm the ABO cell grouping on all units and Rh
grouping on units labeled Rh-neg.
Tests for weak D (Du) are not required to be reported.
The transfusion facility does not need to repeat any other
testing procedure.
13. drmsaiem
Testing of the patient sample.
A record of all results obtained in testing patient samples must be
maintained.
Identification number should be assigned each time a patient is
admitted for treatment.
Any discrepancies between previous and current results must be
resolved before transfusion is initiated.
A new sample should be collected from the patient, if necessary to
resolve the problem.
ABO and Rh grouping results should be included in the file.
Also, notations concerning unusual serologic reactions and the
identity of unexpected Abs in the patient’s serum should be
included.
14. drmsaiem
Testing of the patient sample.
ABO and Rh grouping and Ab screening of the patient’s
serum can be performed in advance of or at the same
time as the cross-match.
If the patient has had a transfusion or has been pregnant
within the last 3 months or if the history is unavailable or
uncertain, the sample must be obtained from the patient
within 3 days of scheduled transfusion.
15. drmsaiem
Testing of the patient sample.
ABO Grouping.
Determination of the patient’s correct ABO group is the
most critical pre-transfusion serologic test.
If the cell and serum grouping results do not agree,
additional testing must be conducted to resolve the
discrepancy.
If the patient’s ABO group cannot be satisfactory
determined and immediate transfusion is essential,
group O packed red blood cells should be used.
16. drmsaiem
Testing of the patient sample.
Rh Grouping.
Rh grouping is performed using anti-D blood grouping
serum. Tube or slide tests should be performed
according to the manufacture’s directions for the
reagent, which may or may not include the use of a
suitable diluents control.
Control must be run in parallel with Rh grouping tests
performed on patient’s samples, to avoid incorrect
designation of Rh neg, patient as Rh positive.
17. drmsaiem
Testing of the patient sample.
Direct antiglobulin test (DAT) should be performed on
the patient’s red blood cells to determine whether uptake
of autoantibody, (alloantibodies, if the patient’s has been
recently transfused) is responsible for the positive
control result.
18. drmsaiem
Testing of the patient sample.
If the Rh group of the recipient can not be determined
and transfusion is essential, Rh negative blood should be
given.
The test for Du is unnecessary when testing transfusion
recipients. Individuals typing as Rh neg in direct testing
should receive Rh-neg blood and those typing as Rh pos
in direct testing should receive Rh pos blood.
As Du are considered Rh pos and may receive Rh pos
blood during transfusion.
19. drmsaiem
Testing of the patient sample.
Antibody Screening.
The patient’s serum or plasma must be tested for
unexpected Abs.
The aim of the Ab screening test is to detect as many
clinically significant Abs as possible.
Clinically significant Abs refers to Abs that are reactive at
37°C or in the DAT or both and are known to have
caused a transfusion reaction or unacceptably short
survival of the transfused red blood cells.
20. drmsaiem
Testing of the patient sample.
Abs Regarded as always being potentially clinically
significant
ABO Rh Kell Duffy Kidd S s U
Abs that may sometime be clinically Significant
Lea p Lua Lub Cartwright.
Abs that rarely, if ever, are clinically significant
Leb Chido/Rodgers (Cha/Rha) York, Sd Xg& Bg
21. drmsaiem
Testing of the patient sample.
Correct ABO grouping results are much more critical to
transfusion safety than Ab screening.
Most Abs, other than anti-A and anti-B do not cause
severe hemolytic transfusion reactions. Thus the vast
majority of patients would not suffer grave consequences
if transfused with blood from ABO group compatible
donor without the benefit of Ab screening tests.
22. drmsaiem
Testing of the patient sample.
2- Testing can be performed well in advance of the
anticipated transfusion, allowing ample time for
identification of unexpected Ab and location of suitable
donor units lacking the corresponding Ag.
Methods used to detect Abs in patient’s sera must
demonstrate all significant coating, hemolyzing, and
agglutinating Abs active at 3 7°C.
23. drmsaiem
Cross-match
The two main functions of the cross-match test can be
cited as,
I- It is a final check of ABO compatibility between donor
and patient.
2- It may detect the presence of an Ab in the patient’s
serum that will react with Ags on the donor RBCs but
that was not detected in the Ab screening because the
corresponding Ag was lacking from the screening cell.
