Crossmatching:Major and Minor Cross matching

Caya, Jay G.Puntukan, Nurdeza N.BSMT-4A

Objectives:To understand the principle of cross match procedure and significance of compatibility tests.

Reference:immediate_spin_crossmatch by marilyncollins (PDF file)Practical Blood banking by Dr. Marwan Ibrahim6. Crossmatch_Carolyn Ragland (PDF file)clin1XM_Terry Kotrla (PDF file)COMPATIBILITY_TESTING_7_8 (ppt)Crossmatching(ppt)

Table of contents:Principle of CrossmatchingCompatibility TestingMajor and Minor CrossmatchingPhases of Crossmatching:Immediate Spin phase (IS Phase) Saline PhaseLISS (Low Ionic Strength Solution) or 22% Bovin Albumin PhaseAnti Human Globulin Phase (AHG/ Coombs Phase)

I- Principle of crossmatching:A compatibility test or crossmatch is a lab procedure to determine before transfusion IF there is serologic compatibility between a blood donor and an intended recipient.

The patient specimen must be less than 72 hours old for compatibility testing so that it represents the current immunologic status of the patient.Negative results are taken to indicate compatibility

Purpose of Crossmatching:Is to PREVENT the TRANSFUSION of INCOMPATIBLE CELLS.The transfused red cells will have an ACCEPTABLE survival rate, and there will be no significant destruction of the recipients own red cells.

Compatibility testingCollecting Patient SamplesHemolyzed 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.

Major and Minor crossmatching

Major crossmatchingRECIPIENT SERUM is tested against donor packed cells to determine if the recipient has preformed antibodies AGAINST any antigens on the DONORS CELLS. This is the required cross-match prior to release of a unit of packed cells.

Minor crossmatchingRECIPIENT RED CELLS are tested AGAINST DONOR SERUM to detect donor antibodies directed against a patient's antigens. This is no longer required. It is assumed that the small amount of donor serum and antibodies left in a unit of packed cells will be diluted in a recipient.

Major crossmatchingThe major crossmatch involves testing the patient's serum with donor cells to determine whether the patient has an antibody which may cause a hemolytic transfusion reaction or decreased cell survival of donor cells.

Phases of Major Crossmatching

Immediate Spin Phase (Saline Phase)LISS (Low Ionic Salt solution) 22% Bovine Albumin PhaseAHG Phase or (Coombs Phase)

Note: In blood bank we put step 2-3 in one step and for agglutination once.

I- Immediate Spin Phase(Coombs Phase)

I- Immediate Spin Phase1st wash the donors cell with 0.9 % NSS and make a 3-5 % cell suspension.

*WHY???*WashingTo help remove unwanted antibodies or antigens which may interfere with agglutination reaction.

Saline solution / 0.9 % NaCl- To maintain osmotic balance and prevent the RBC from shrinking (if NaCl is less than 0.9%), or swelling up or get burst, which will interfere with agglutination reaction.

WHY???*3-5 % cell suspension- Make the Ab/Ag reaction more clear, and to avoid false ve and false +ve results.

Procedure:1. Add the following to each labelled crossmatch tube:-2 drops of patients plasma or serum-1 drop of the donor cell suspension2. Mix the contents of each tube.3. Centrifuge tubes for 15 secs 3000 rpm.4. Examine for hemolysis. Record if present.5. Immediately resuspend the cells by gentle agitation; examine the tubes macroscopically for agglutination.6. Grade and record results.

No agglutination = compatible

Results:Any DEGREE OF AGGLUTINATION OR HEMOLYSIS in the crossmatch tubes during ANY phase indicates INCOMPATIBILITY and the blood should not be given. If AGGLUTINATION OR HEMOLYSIS occurs in the screen cells tubes, this indicates the presence of an atypical antibody and further testing must be done.

II- LISS or Bovine Albumin Phase

WHY??solutions such as albumin, polymerized albumin or low ionic salt solutions (LISS) are frequently employed to: increase the sensitivity of the crossmatch or to reduce the incubation time. By lowering the ionic strength or increasing the dielectric constant of the test medium, these solutions increase antibody uptake and enhance the strength of the antigen-antibody reaction.

II- LISS or Bovine Albumin PhaseProcedure:In the same tube just add 2 drops of albumin, /polymerized albumin or low ionic salt solutions (LISS).Incubate @ 37C for 20 mins.Wash atleast 2 times.

III- AHG PHASE

*WHY???*To detect incomplete antibody like Ig G.

III- AHG PHASEProcedure:After incubating add 2 drops of AHG reagent.Centrifuge for 15 secs.Record the result

Checking the crossmatch if it is valid using check cells.

ProcedureJust add 1 drop of check cells to the same tube.Centrifuge for 15 secs.Record the result.

Note: atleast 2+ agglutination must be observed to the crossmatch was valid.

For you to understand clearly lets watch a video

Evaluation:What is the Principle of crossmatching?What is the purpose of detecting Ig G in AHG phase?What is the primary purpose of crossmatch procedure?What is the maximum amount of time a specimen may be used for pretransfusion testing?

Evaluation:How is the interpretation of results in crossmatching?