Transfusion Lab Exam Flashcards
What are the 7 controls of tubes?
Coloured reagents
Anti-AB
X2 anti-Ds
Rh Control
Reverse group to confirm group
A1 and B cells to control forward
By typing the A1 and B cells you are controlling the Reverse group as well
What are the most common blood groups in Caucasians?
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In notes
What are the most common Rh phenotypes in Blacks
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Principle of the Antiglobulin Test/Coombs test
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Direct vs indirect IAT
Direct:
- rbcs sensitised in vivo
- addition of AHG brings about agglutination
- detection of in vivo sensitised rbcs
Indirect:
- patient plasma containing antibodies is incubated with reagent rbcs
- sensitisation of reagent rbcs occurs but no agglutination (igG too small to form bridges)
- addition of AHG allows for agglutination of sensitised IgG coated rbcs
What would cause a rh control to be positive
DAT positive
Rouleaux
Cold ags
What would cause a rh control to be positive
DAT positive
Rouleaux
Cold ags
What might cause rouleaux
Elevated levels of globulin
- multiple myeloma
- Hodgkins lymphoma
How would you resolve missing antibodies?
Double concentration of plasma used
Carry out testing at 4 degrees (cool serum to 4 degrees) as ABO antibodies prefer cold temps
What are some examples of cold antibodies?
M or N
H
I
P
Lewis
Anti A1
What are alloantibodies
Antibodies made against foreign cells e.g P1 or anti-M
What are auto antibodies, how are they detected, how are they resolved?
Antibodies made against ones own red cells
Cold reacting antibodies that cause agglutination with red cells at room temperature or below
Will cause a positive auto
Resolved by warming tubes to 37 degrees and washing red cells
What is adsorption?
An antibody with its antigen treated under optimal conditions so that the antibody will attach to the antigen, thereby removing the antibody from the serum
I.e. patient plasma mixed with reagent red cells displaying antigen in optimal conditions so that the antibody is adsorbed onto the red cells leaving the plasma free of the antibody
What is elution?
Whereby cells coated with antibody are treated to disrupt the bonds between antibody and antigen.
The free antibody is then collected in an inert diluent such as saline or 6% albumin and tested with reagent cells for specificity
Red cells coated in antibody, acid elation, saline displacement, antibody now present in saline
How would you resolve a query acquired B?
React patients anti-B with their own red cells, it won’t go positive
An anti-B which doesn’t react with acquired B is produced by some manufacturers but not available in standard labs
Incubating with acetic anhydrate will re-acwtylate the acquired B back to A
