BMS 185 Final (2nd half :p ) Flashcards
What is Antigen Phenotyping?
Looks at the antigen on the patient’s RBCS
When do you do Antigen Phenotyping?
- If the patient has an antibody, you phenotype for the corresponding antigen, to make sure the patient does not have it
1a. For example, if the patient has an anti-Jkb then when you phenotype for Jkb the result should be 0 (antigen not present) - Can phenotype RBC units to find one that does NOT have the antigen that the patient made an antibody to
2a. (general donor blood phenotyping for lack of antigen that the patient has an antibody for)
What type of control(s) are necessary when phenotyping?
Positive and Negative Control
What is a mixed field reaction?
two different cell populations together in circulation
- You can phenotype a patient, unless they have what?
- What would be their result?
- if they have been transfused within 90 days
- mixed field reaction
Why do you use heterozygous cells for phenotyping positive controls?
We use heterozygous cells because we want to pick up the weakest expression of the antigen for the positive control
What is heterozygous?
two different alleles present together
(Example: C+c+)
What is homozygous?
only one allele present
(Example: C+ c 0 or C 0 c+)
What type of reagent red cell expression is chosen for a positive phenotyping control?
heterozygous
What type of reagent red cell expression is chosen for a negative phenotyping control?
homozygous
How many RBC units do you need to phenotype to find a compatible unit?
Number of requested RBC units divided by the frequency of the antigens not present
- Example: If you have an anti-K and anti-E with a request of 6 units. K antigen is present on 9% and E antigen is present on 30% of the population
- 6 units/ (.91) x (.70) = 9.41915
- Always round up! So screen 10 units to find 6 that are K and E negative
What antibodies are IgM?
anti-Lea, anti-Leb, anti-M, anti-N, ABO antibodies (anti-A, anti-B),anti-P
(LMNOP [ ABO = O] [L = Lewis])
What’s another name for IgM?
cold antibodies
Is IgM small or large? And can it pass the placenta and cause HDFN?
- Large
- IgM cannot cross the placenta
Is IgG small or large? And can it pass the placenta and cause HDFN?
- Small
- IgM can cross the placenta and can cause HDFN
What antibodies are IgG?
Rh Group, Kell group, Duffy group, Kidd Group, anti-S, anti-s
Does Ficin impact antibodies or antigens?
antigens
What is ficin?
Enzyme that is used to treat reagent RBCs to help us identify antibodies
If an antigen is destroyed by ficin, what reaction would be present for the destroyed antigen?
negative, due to lack of antigen for the antibody to bind to
What antigens are DESTROYED by ficin?
M, N, Fya, Fyb, S,s, and Xga antigens
(MNSs, Duffy, Xga)
What antigens are ENHANCED by ficin?
Rh group, Kidd Group, Kell Group, Lewis Group, Lutheran Group, P
What antigens are UNEFFECTED by ficin?
kell group
What are the steps to doing a panel?
1. RULE OUTS (No Reaction, Homozygous rules outs)
1a. Exception: Kell can be be ruled out heterozygously
2. If more than 1 not ruled out, run select cells
(2a. Example if you suspect an anti-Fyb and can’t rule out E. You would choose a panel cell that is negative for Fyb and homozygous for E (Fyb 0 and E + e 0). You would also pick a Fyb + cell to run as your positive control, Hopefully, the select cell would be negative and you can officially rule out E )
2b. Optional: If you have the patient’s phenotype and the auto control is negative then you can rule out based on patient’s phenotype
3. RULE INS
3a. Once you know which antibody is present on the reactive cells circle the phenotype (+) that tells us the antigen is there
To crossmatch a patient, you need # blood types from # different signed EDTA (pink or purple top tubes) specimens before we can give out any blood products
2, 2
What are the different types of crossmatching?
- Single electronic
- Immediate Spin Crossmatch
- full crossmatch
What are the different types of crossmatch?
- Single Electronic Crossmatch
- immediate spin crossmatch
- full crossmatch
What screen and history is needed for a Single Electronic Crossmatch?
- Negative Antibody Screen
- No history of antibodies
What screen and history is needed for a Immediate Spin Crossmatch?
- Negative Antibody Screen
- No history of antibodies