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Pretransfusion Compatibility Testing

What is in a crossmatch order? ABO, Rh typing and antibody screen.
When is weak D testing not necessary? For transfusion patients who type as Rh negative. Use Rh neg donor for transfusion.
What is the purpose of an antibody screen? To rule out any unexpected antibodies to blood groups other than ABO.
What type of cells are tested in a panel. O neg cells.
What is the Rule of Three? If plasma reacts with 3 antigen positive cells and does not react with 3 antigen negative cells, there is a 95% probability the identification did not happen by chance.
Formula for calculating number of units to be screened: N = # units needed / negative frequency of antigens
Time of specimen if patient was transfused or pregnant in last 3 months Specimen must be <3 days old
What is an autologous donation? Unit donated by self.
What is a directed donation? Unit donated for a patient by a relative or friend.
What is the order of transfusion? Autologous, directed, then random
Antibody screen is negative Proceed with Immediate spin or electronic crossmatch
Antibody screen is positive Set up antibody panels
When is reverse ABO typing not performed? neonates
What is the AABB requirement for all antibody screen? 37C incubation and AHG phase
What is the purpose of add check cells? To make sure AHG reagent was added.
Advantages of Gel Method Stable for 24 hours; can read at a later time; results more objective; automation
How to resolve Rouleaux in gel system? Use tube AHG method. Saline replacement technique for 37C phase.
In solid phase, what is a positive reaction? Diffuse pattern in well.
In solid phase, what is a negative reaction? Pellet in bottom of well.
What should be done after a antibody screen? Type the patient for the antigen in question. It should be negative for that antigen.
What is the universal donor type? O cells
What are compatible pack cells for patient type A? A, O
What are compatible pack cells for patient type B? B, O
What are compatible pack cells for patient type AB? AB, A, B, O. AB type is universal recipient.
what does crossmatch refer to? Incubation of patient's plasma with donor cells.
Immediate spin crossmatch 2 drops of patient's plasma + 1 drop of donor 2-5% cells, centrifuged immediately, and read for hemolysis and agglutination. Neg reaction indicates compatibility.
What is the purpose of IS crossmatch? final check of ABO compatibility between donor RBC and patient's plasma
What are the advantages of IS crossmatch? Saving time for crossmatch procedure. Fewer units are needed for advance crossmatching, esp. for surgeries.
What are the disadvantages of IS crossmatch? Positive reactions are seen in presence of other non-ABO RT reactive antibodies or rouleaux.
Name 3 ways to resolve incompatibilities in the crossmatch? 1) resolve pos result by ruling out ABO incompatibility 2) perform RT panel to ID presence of cold reactive antibody 3) Resolve rouleaux by repeating IS crossmatch with saline replacement technique.
AHG crossmatch Patient plasma is mixed with donor cells as in IS crossmatch, potentiator is added, incubated at 37C and preform AHG test.
If positive incompatible crossmatch AHG perform DAT on donor RBC. If pos, that donor's RBSs are already coated with IgG and/or complement. Remove DAT-pos donor RBC from inventory.
If patient's antibody screen is neg and only one donor unit is incompatible suspect presence of antibody to low-incidence antigen on donor RBC
Created by: 3215525