10 Compatibility Testing

• Compatibility testing is a collection of different processing; a series of testing procedure and processes with the ultimate objective of ensuring best possible result of a blood transfusion
• Strict adherence to and application of each parameters of compatibility is imperative to the management of safe blood transfusion.
• ABO/Rh is the foundation of compatibility testing.

  • If you’re donor and recipient are not match, there is no sense of continuing compatibility testing
• Serological crossmatch phases:

  • Immediate spin or saline phase
  • 37°C or Thermophase
  • AHG phase
• Major Crossmatch is routinely perform in laboratory

  • Patient serum + Donor Red Cell
  • Generalized antibody screening – what antibody is present.
  • We look for antibodies against donor red cell
• Minor Crossmatch is widely replace by antibody screening
• Antibody screening or alloantibody identification looks for alloantibody in the patient serum or plasma

  • We can identify antibodies present in the patients serum that could potentially react with your donor red cells
• Clerical error is the major cause of transfusion associated fatalities (greatest test)
• Common causes of errors:

  • Misidentification of recipient – pre-analytical error
  • Mix-up of samples during processing – analytical error
  • Misidentification of recipient when transfusion is given – post-analytical error
• Patient’s wristband ID must always be compared to requisition form
• Ideally, serum is the preferred sample for blood bank
• Incompatible crossmatch is indicated by agglutination and that means that there is antibodies against the red cell → can be seen in serum or plasma.
• Hemolysis is a false positive error
• Patient with hemolytic anemia is not rejected
• Samples in BB are usually in red top tube because tubes with clot activators might contaminate the serum and can cause false agglutination.
• In blood bank, tubes used are:

  • Purple / lavender EDTA - is used in hematology section
  • Pink EDTA – is specific for blood bank
• Donor sample must be collected at the same time as the full donor unit
• Donor information/medical history card, pilot samples and collection bag must be labeled with the same unique numbers before starting the phlebotomy
• RBCs for donor pre-transfusion testing can be prepared from segmented tubing through which donor blood was collected
• Using a heat sealer, we segment the tube and each segment can be used for testing.

  • Note: donor and recipient samples must be stored for a minimum of 7 days post transfusion (stoppered, labeled 1-6°C) in relation to transfusion reaction
• Serological testings:

  • DONOR → ABO, Rh, test for blood-borne diseases
  • RECIPIENT’S → ABO, Rh, unexpected clinically significant antibodies
• Serological crossmatch purpose is for primary test for determining whether the patient has antibodies against donor red cell

  • Patient serum + donor RBC
• Immediate Spin Phase

  • PSDR + quick centrifugation (20-30 sec)
  • Absence of agglutination or hemolysis indicates compatibility
  • IgM antibodies was detected because of room temperature → False reactions may be seen in other IS reactive antibodies (cold agglutinins)
• 37°C phase

  • PSDR incubate for 15-30 mins at 37°C
  • centrifuge (no agglutination proceed to next step)
  • Antibody detected is IgG because they react at warm temperatures
• AHG Phase

  • PSDR + Immediate Spin + 37°C + AHG
  • Enhancement media may be applied
  • LISS, BSA, PEG
  • Absence of agglutination or hemolysis indicates compatibility
  • Need of washing to remove unbound antibodies
• Donor’s autoimmune condition can cause false positive
• If the patient has a high gamma globulin or the patient has a multiple myeloma, the results will be false agglutination
• Antibody screening

  • Recipient’s serum or plasma
  • To detect as many clinically significant unexpected antibodies antibodies as possible (IgG, 37°C AHG)
  • Clinically significant antibodies are reactive at 37° and have cause HTR, HDN
• Some labs employed shortened incubation time and enhancement medium to accelerate Ag-Ab reaction, which may result in false negative
• In extreme emergencies, Group O Rh negative PRBC (universal) may be used.
• Resorting to Rh positive is best made immediately if patient is a man or woman beyond child bearing age

  • Men are not at risk of developing transfusion reaction
• Administration of RhIg is to prevent anti-D formation after crisis has been resolved
• Compatibility testing in Plasma product

  • not required– no RBC
  • Donor plasma + recipient’s RBC
  • To detect ABO compatibility