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
What is Whartons jelly, how do we detect it, how do we resolve it?
Gelatinous substance from ct of cord blood
Causes false agglutination
Wash rbcs 6 times or request heel blood sample
How do we resolve rouleaux?
Froward group: wash cells to remove protein and repeat tes
Reverse group: saline replacement, Incubate reagent rbcs with patient plasma, centrifuge down, remove supernatant, replace with saline, spin again and examine again for agglutination
What 3 cells usually make up an antibody screen?
R1wR1
R2R2
rr
*all must be group O
What controls do you use for an AB screen?
Weak anti-D
Inert AB
What are the 13 criteria of AB screening cells?
Group O cells
Minimum R1wR1, R2R2 but rr usually included
Should express red cell antigens and should be typed e.g. Fya+Fyb-
Not pooled
DAT negative
Homozygous for Duffy, Kidd and S/s
A single K pos cell
Negative for low incidence antigens
Negative for HLA ag e.g. Bg
Preservative: Na azide
Lot number
Expiry
Double typed with 2 different antisera
What systems are enhanced by enzymes?
ABO/H
Rh
Kidd
Lewis
I
P1PK/GLOB
What systems are decreased by enzymes?
MNS
Duffy
What system is unaffected by enzyme
Kell
How do you carry out antibody panel in gels?
Add 50ul red cell to well
Add 25ul plasma to well
Incubate at 37 degrees for 15 mins
Centrifuge for 10 mins
What is the dosage affect?
The effect of seeing stronger reactions with homozygous antigen expression compared to heterozygous expression
E.g. anti-Jka may react stronger with Jk(a+b-) compared to Jk(a+b+)
What would cause a positive DAT
HDN
HTR
AIHA
Positive donor cells in crossmatcj: non pathologic - complement related
What are the three types of crossmatch
Electronic issue
IAT (on bench)
Immediate spin - ABO check
What are the requirements for electronic issue?
Group confirmed unit
2 samples on patient
No previous antibody positive
No anomalies/manual input etc
Positive patient ID on Blood Track
What are the rules of sample validity?
Sample valid for 72 hours (generally applied in all hosps)
Guidelines:
- 72 hours validity if patient has been tranafused/pregnant in last 3 months
- 7 days if patient has no been transfused/pregnant in last 3 months
How long can you keep patient plasma?
Can be kept for 3 months if kept frozen at -30 degrees
How do you perform a crossmatch?
Add donor rbcs (50ul) and patient plasma (25ul) to AHG gell card
Incubate + centrifuge
How do you preform a DAT
(4)
Add 50ul patient rbcs to AHG gel
Use IgG sensitised cells as +/ve ctrl
Use OR1r cells as -/ve ctrl
No incubation, centrifuge and read
Rh phenotype frequencies
Caucasians: R1, r, R2, R0
Blacks: R0, r, R1, R2
Rare: r’, r’’, Rz, ry
Gel quantities
Typing: forward = 10ul rbcs, reverse = 50ul cells + 50ul plasma
Antibody screen: 50ul rbcs, 25 plasma
Crossmatch: 50ul rbcs, 25ul plasma
DAT 50ul rbcs
