lecture 10 blood bank Compatibility Testing Dr. Dalia Galal

What is compatibility testing? Also called pretransfusion testing Purpose: To select blood components that will not cause harm to the recipient and will have acceptable survival when transfused

Compatibility testing? There are several components of compatibility testing Proper specimen collection Reviewing patient transfusion history ABO, Rh, and antibody testing (screen/ID) Crossmatching Actual transfusion

Compatibility testing Can be divided into 3 categories: Preanalytical procedures Serological testing Postanalytical procedures

1- Pre-analytical phases Patient and sample identification Specimen collection Review of patient history

A- Patient and sample Identification Full patient name and hospital number Name of physician Date and time of collection All of this should be on the request form and the sample

Specimen Tubes Pink Top - EDTA Red Top – no additives

B- Specimen Collection Collected in tube with EDTA or no additives If the venipuncture causes hemolysis, the sample may be rejected True hemolysis in the patient is the result of complement activation Testing should be performed on samples less than 72 hours, otherwise, complement dependent antibodies may be missed (complement can become unstable)

C- Review of patient history Look at recipient’s records for any prior unexpected antibodies Previous transfusion reactions

2- Serological Testing ABO/Rh Antibody detection/identification 3 tests: ABO/Rh Antibody detection/identification Crossmatch

ABO/Rh Typing In the ABO typing, the forward and reverse MUST match In the Rh typing, the control must be negative Both of these will indicate what type of blood should be given

Antibody screen and/or ID The antibody screen will detect the presence of any unexpected antibodies in patient serum If antibodies are detected, identification should be performed using panel cells (with an autocontrol) If an antibody is present, units negative for the antigen must be given (remember the calculation?) Proceed to the cross match…

Crossmatching Purpose: Prevent transfusion reactions Increase in vivo survival of red cells Double checks for ABO errors Another method of detecting antibodies

Crossmatch Crossmatch Two types of crossmatches Major – routinely performed in labs Minor – not required since 1976 Crossmatch No agglutination ~ compatible Agglutination ~ incompatible Donor RBCs (washed) Patient serum

Units of whole blood with segments attached

Procedure ABO/Rh typing is FIRST performed With anti-A, anti-B, anti-D With A1 cells and B cells Antibody Screen is performed next With screening cells

Crossmatch Procedure If antibodies are NOT detected (in antibody screen test): Only immediate spin (IS) is performed using patient serum and donor blood suspension This fulfills ABO incompatibility This is an INCOMPLETE CROSSMATCH If antibodies ARE detected (in antibody screen test): Antigen negative units found and X-matched All phases are tested: IS, incubate at37°, antihuman globulin (AHG) This is a COMPLETE CROSSMATCH

Will Not (disadvantages) Crossmatches… Will (advantages) Verify donor cell ABO compatibility Detect most antibodies against donor cells Will Not (disadvantages) Guarantee normal survival of RBCs Prevent patient from developing an antibody Detect all antibodies Prevent delayed transfusion reactions Detect ABO/Rh errors

Incompatible crossmatches Antibody screen Crossmatch Cause Resolution Pos Neg Antibody directed against antigen on screening cell ID antibody, select antigen negative blood Antibody directed against antigen on donor cell which may not be on screening cell OR donor unit may have IgG previously attached ID antibody, select antigen negative blood OR perform DAT on donor unit Antibodies directed against both screening and donor cells Antibody ID, select antigen negative blood

Post-analytical phase Involves labeling, inspecting, and issuing the blood unit Labeling form includes patient’s full name, ID number, ABO/Rh of patient and unit, donor #, and compatibility results. Form is attached to the donor unit and only released for the recipient The unit is visually inspected for abnormalities, such as bacterial contamination, clots, etc

Bacterial contamination This unit shows bacterial contamination and should NOT be given to the patient The plasma in the samples is fine, but the plasma in the unit shows heavy hemolysis from bacteria

Issuing blood When it’s time to release a blood product to the nurse or physician, a few “checks” must be done Requisition form Comparing requisition form  donor unit tag  blood product label Name of persons issuing and picking up blood Date and time of release Expiration date

What if the unit is unused? Blood can be returned if it is not needed for transfusion Unit closure has to remain unopened Storage temperature must have remained in the required range (1° to 10°C for RBCs) If not at correct temp, unit must be returned within 30 minutes of issue