COMPATIBILITY TESTING

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COMPATIBILITY TESTING

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

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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.

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Patient red cell with D Ag.
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If Rh ve do
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