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COMPATIBILITY TESTING

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COMPATIBILITY TESTING Dr. MOHAMMED H SAIEM ALDAHR BLOOD BANK 3RD MEDICAL TECHNOLOGY COMPATIBILITY TESTING Out line Collection and Preparation of Samples Collecting ... – PowerPoint PPT presentation

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Title: COMPATIBILITY TESTING


1
COMPATIBILITY TESTING
  • Dr. MOHAMMED H SAIEM ALDAHR
  • BLOOD BANK
  • 3RD MEDICAL TECHNOLOGY

2
COMPATIBILITY TESTING
  • Out line
  • Collection and Preparation of Samples
  • Collecting Patient Samples
  • Donor Samples
  • Selection of Appropriate Donor Units
  • Testing of the donor sample
  • Testing of the patient sample
  • Cross-match
  • Summary of Pre-transfusion Testing

3
COMPATIBILITY TESTING
  • As the knowledge of new blood group system
    increased, so did the search for more sensitive
    pre-transfusion compatibility testing methods.
    Pioneer blood bankers mixed the patients serum
    and the donors red cells and observed for direct
    red blood cells lysis, agglutination, or both.
    This became known as the major cross-match test.
  • The term compatibility test and cross-match are
    some times used interchangeably, they should be
    clearly differentiated.

4
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 donors and
    patients 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 recipients own red cells.

5
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.

6
COMPATIBILITY TESTING
  • To prevent collection of samples from the wrong
    patient, the blood request form must be used to
    confirm the patients identity before phlebotomy
    is performed. The request form must state the
    intended recipients 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.

7
COMPATIBILITY TESTING
  • The patients wrist band identification must
    always be compared with the requisition form.
  • If the patient does not have a wristband or if
    the patients identity is unknown, some form of
    positive identification must be attached to the
    patient before collection of samples.

8
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.

9
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.

10
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.

11
COMPATIBILITY TESTING
  • Donor and recipient samples must be stored for a
    minimum of 7 days following transfusion.
  • The samples should be stoppered and refrigerated
    at 1-6C, carefully labeled, and adequate in
    volume so that they can be re-evaluated if the
    patient experiences an adverse response to the
    transfusion.

12
Compatibility Testing Protocols.
  • Selection of Appropriate Donor Units.
  • In almost all cases, blood and blood components
    of the patients own ABO and Rh group should be
    selected for transfusion.
  • When blood and blood components of the patients
    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.

13
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 patients 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.

14
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

15
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.

16
Selection of Appropriate Donor Units.
  • Rh-pos blood should not be given to Rh-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.

17
Compatibility Testing Protocols.
  • Testing of the donor sample.
  • According to the Code of Federal Regulation (CFR)
    and the American Association of BB (AABB)
    standards, ABO and Rh grouping (including a test
    for weak D) and tests intended to prevent disease
    transmission must be performed on a sample of
    blood taken at the time of collection of the unit
    of blood from the donor.
  • A screening test for unexpected antibodies to red
    blood cell Ags is required by AABB standards on
    samples from donors revealing a history of prior
    transfusion or pregnancy.

18
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.

19
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 patients serum should be included.

20
Testing of the patient sample.
  • ABO and Rh grouping and Ab screening of the
    patients 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.

21
Testing of the patient sample.
  • ABO Grouping.
  • Determination of the patients 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 patients ABO group cannot be satisfactory
    determined and immediate transfusion is
    essential, group O packed red blood cells should
    be used.

22
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 manufactures
    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 patients samples, to avoid
    incorrect designation of Rh neg, patient as Rh
    positive.

23
Testing of the patient sample.
  • Direct antiglobulin test (DAT) should be
    performed on the patients red blood cells to
    determine whether uptake of autoantibody,
    (alloantibodies, if the patients has been
    recently transfused) is responsible for the
    positive control result.

24
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.

25
Testing of the patient sample.
  • Antibody Screening.
  • The patients 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 37C 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.

26
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

27
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.

28
Testing of the patient sample.
  • Detection of unexpected Abs is important,
    however, for the selection of donor red blood
    cells that are likely to survive maximally in the
    patient circulation.
  • Weakly reactive Abs that are capable of reacting
    with their Ags at 37C can cause decreased
    survival of transfused incompatible red cells.

29
Testing of the patient sample.
  • Because large numbers of Ab molecules are present
    in the patients circulation compared with the
    number of red cells in a unit of blood,
    incompatible donor cells are highly vulnerable to
    destruction by patient Abs.
  • Abs screening offers several advantages over
    direct cross-matched testing for detection of
    Abs
  • 1- Testing is performed using selected group O
    red cells that are known to carry optimal
    representation of important blood group Ags.

30
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 patients sera must
    demonstrate all significant coating, hemolyzing,
    and agglutinating Abs active at 3 7C.

31
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
    patients 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.

32
Cross-match
  • Major and Minor cross-match tests
  • Major cross-match test, consisting of mixing the
    patients serum with donor RBCs.
  • Minor cross-match test, consisting of mixing the
    donors plasma with patients RBCs
  • The minor cross-match test has been completely
    eliminated in most blood banks, because donor
    samples are screened beforehand for the more
    common Abs.

33
Cross-match
  • Method for major cross-match tests.
  • Cross-match methods can be categorized by the
    test phase in which the procedure ends.
  • Immediate spin (IS) cross-match (Abbreviated
  • Cross-match)
  • When no clinically significant Abs are detected
    nor are there previous record of such Abs, a
    serologic test to detect ABO incompatibility is
    sufficient.

34
Cross-match
  • In IS (the patients serum with donor cell are
    centrifuge immediately) absence of hemolysis or
    agglutination indicates compatibility.
  • False reaction may be seen in the presence of
    other IS reaction (auto -I). In patient with
    hyperimmune ABO Abs, when the procedure is not
    performed correctly (delayed in centrifugation or
    reading) when rouleauex is observed, or when
    infants specimens are tested.

35
Cross-match
  • Antiglobulin Cross-match
  • The procedure begin in the same manner as the IS
    cross-match, continues to 37C incubation and
    finishes with AHG test.

36
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37
SUMMARYPRE TRANSFUSION TESTING
  • Is to provide safe, compatible blood for
    transfusion to each individual patient. The steps
    necessary for safe transfusion are
  • 1. Accurate ABO and Rh typing of the patient.
  • 2. Accurate ABO and Rh typing of the donor.
  • 3. Screening tests for antibodies in the donors
    and patients serum.
  • 4. In the presence of patient antibodies,
    selection of appropriate units for each patient.
  • 5. Compatibility Testing - (Major)
  • 6. Accurate completion of paperwork and labels

38
PRE TRANSFUSION TESTING
  • Compatibility Testing
  • Each compatibility test is a unique experiment
    in which an unknown (patient) serum and (donor)
    red cells are tested for the detection of
    unexpected antibodies which are directed against
    antigens found on the cells. Negative results
    indicate compatibility. This is one of the most
    important tests performed by a transfusion
    service.

39
PRE TRANSFUSION TESTING
  • The purposes of compatibility testing are
  • 1. To detect irregular antibodies in the
    recipient serum that are directed against the
    donors cells.
  • 2. To detect errors in ABO grouping.
  • 3. To detect errors in labeling, recording, or
    identifying donors or recipients samples.

40
PRE TRANSFUSION TESTING
  • Compatibility testing does not
  • 1. Ensure normal survival of donor red cells.
  • Prove that donor and or recipient serum is free
    of antibodies. Prevent immunization of the
    recipient.
  • Detect ALL ABO typing errors.
  • Detect errors in Rh typing of either recipient or
    donor unless the recipients serum contains an Rh
    antibody.
  • Detect ALL error of identification.
  • Pre-transfusion testing of the recipient must
    include an ABO and Rh typing, antibody screen,
    and a cross-match with all donor units.

41
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42
Patient red cell with D Ag.
43
If Rh ve do
44
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