Compatibility Testing Flashcards
What symptoms should a patient be showing to get a blood transfusion?
Symptoms of decreased oxygen-carrying capacity
What 3 kinds of conditions make people transfusion candidates?
Decreased production of RBCs (e.g., leukemia, bone marrow failure, and chronic anemia).
Increased destruction of RBCs (e.g., hemolytic anemia).
Loss of RBCs (e.g., traumatic bleed, surgical blood loss)
What is the definition of compatibility?
The ability of donor cells and proteins to survive in the recipient’s circulation for an expected length of time without evoking an immune response
What is the purpose of compatibility testing?
To provide compatible blood for patients who require or may require a transfusion
What is the limitation of compatibility testing?
Testing can only prove that there is no obvious incompatibility. Reactions can appear negative due to antibody’s falling below detectable levels, or the corresponding antigen is absent from screening cells. Also, the recipient can get sensitized to donor antigens during a transfusion.
What are the three methods of cross-matching?
Immediate Spin
IAT or MTS
Electronic
What qualifies a patient for an electronic cross-match?
Their ABO and Rh group must have been typed at least twice by 2 different MLTs. They must not have any antibodies.
What safeguards are in place for electronic cross-match?
The computer won’t allow the use of a donor until it’s ABO and Rh group are verified, and it will not allow the issue of ABO and Rh incompatible blood
What does a negative/compatible cross-match result look like?
No agglutination or hemolysis
What must you do if the patient needing a transfusion has a positive antibody screen?
Check their history for a previous transfusion or pregnancy, and a previously identified antibody. The antibody (s) must be identified and the patient must be phenotyped.
What is the Antigen Frequency Calculation used for?
To determine how many units are required for testing before finding compatible units. Used for patients who have a positive antibody screen and/or have a history of having an antibody
How is the crossmatch procedure different for a patient with a negative antibody screen but with an antibody history compared to a patient with a positive antibody screen?
You need to report that the previously identified antibody was not detectable. Don’t report that the screen was negative.
When do you need to repeat RA/RB on a patient sample in a crossmatch?
If you retrieve the sample from storage
Why can’t we accept hemolyzed samples for crossmatch?
Hemolysis can mask the detection of antibody-induced hemolysis
Why can’t we accept samples diluted with IV fluids for crossmatch?
Because they are diluted, we could miss a weak antibody or a false positive reaction could happen because of the molecules in the IV fluid
How do you do the calculation for determining how many units you should test for a crossmatch?
of units = # of units required/frequency of antigen negative blood
If you’re looking for a patient with more than one antibody, you multiply the frequencies together.
If the patient has an antibody or a history of one, how many units must we have minimum available for their entire hospital admittance?
2 units
How long is the neonatal period for transfusion purposes?
Birth to 4 months of age
What should you do for a routine transfusion of a neonate?
Give irradiated and <7 day old blood
What ABO and Rh group is usually selected for neonatal transfusion?
O Rh Negative
What can you do for a neonatal transfusion in an emergency situation?
You can use non-irradiated blood that is 14 days old (WBC will be nearly non-viable)
For neonates, what kind of specimen is used to test for unexpected antibodies?
Maternal plasma
What kind of specimen is used for crossmatch testing of a neonate?
Venous or capillary blood. Can crossmatch with maternal plasma if required.
What must be true to issue blood for a neonatal transfusion without crossmatching?
Maternal antibody screen is negative
Infant’s DAT is negative (or positive if ABO incompatible)
