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
What does a Immediate Spin Crossmatch do?
catch an ABO incompatibility
What does a Single Electronic Crossmatch do?
The computer checks ABO compatibility between patient and donor unit
What does a Full Crossmatch do?
Makes sure the RBC unit you choose needs to lack the antigen that the patient has an antibody against
(For example, if the patient has an anti-K then you need to phenotype the donor unit to make sure it’s K 0)
What screen and history is needed for a Full Crossmatch?
- Positive Antibody Screen
OR - Negative Antibody Screen with a history of antibodies
What is Rhogam?
artificially made passive anti-D that is given to labor and delivery patients so that the mother doesn’t make a real anti-D
What are the three things necessary to be a candidate for Rhogam?
- Rh Negative
- No real anti-D (not sensitized)
- Baby is Rh Positive
How much does 1 vial of Rhogam cover in a fetal bleed?
a 30mL fetal bleed
When does a pregnant person receive Rhogam?
- If the mother was in a traumatic even, the doctor can prescribe Rhogam (ex. car crash)
- Rh mothers will receive 1 dose of Rhogam ~28 weeks (regardless of baby’s ABH type)
- During delivery, if the baby is Rh positive
At delivery, if the baby is Rh positive, what determines how much Rhogam is given?
Fetal Screen and KB test
How much Rhogam is given if the fetal screen is negative?
1 vial of Rhogam
What must be done, if the fetal screen is positive?
KB test is done to calculate the amount of Rhogam needed
What happens when the baby’s RBCs are destroyed?
- A drop in the baby’s hemoglobin and hematocrit
- An increase in bilirubin, potential Kernicterus
What is Kernicterus?
bilirubin gets into the brain and causes severe brain damage
What are the criteria for pedi packs?
- O+ or O- units
- irradiated
- hemoglobin S negative
- cytomegalovirus (CMV) negative
- fresh units (collected in the past 7 days)
How do you treat a drop in the baby’s hemoglobin and hematocrit?
- Transfuse the baby via syringe
- Pedi packs
How do you treat the baby if they have an increase in bilirubin?
placing the baby in UV light can lower bilirubin levels
If the mom is type O, there will be a possibility of ABO incompatibility if the baby is…
A, B, or AB
If the mom is Rh negative, there will be a possibility of ABO incompatibility if the baby is…
Rh positive
When finding out a baby’s blood type, why do we only look at the front type?
humans do not start making ABO antibodies until 4 months old
When do we test the CORD specimen?
When mom is both type O and/or Rh negative
What is the procedure for a CORD specimen?
- Blood type the baby (front type)
- Perform a DAT (1 tube) with monoclonal anti-IgG
- If the DAT is positive, you must call as a critical result, and send plasma to chemistry for a bilirubin test
All ABO antibodies are IgM, except…
sometimes type O individuals will have anti-A and Anti-B IgG
(this is dangerous, b/c those few IgG ABO antibodies can cross the placenta and cause mild HDFN)
What do you do when the pregnant person has a clinically significant IgG antibody (such as Rh group, Kell, Kidd, etc.) that can cause HDFN?
you monitor the pregnant person throughout the entire pregnancy by checking if the antibody has a significant spike/increase in titer
When is a fetal cell screen performed?
Rh negative Pregnant person gave birth to a Rh positive baby (possibility of a fetomaternal hemorrhage)
What is being tested in the fetal cell screen?
pregnant person’s RBC
What is the procedure for fetal cell screen?
- Add anti-D antisera to Mom’s RBC
(detects Rh positive baby cells present in mom’s circulation) - Wash 6x (remove unbound anti-D)
- Add indicator to form a pink rosette (binds to any baby RBC+anti-D complex)
What is considered a POSITIVE fetal screen?
Within 5 microscopic fields, there are 5+ rosettes
Are fetal screens qualitative or quantitative?
QUALITATIVE
Is Kleihauer Betke Test (KB Test) qualitative or quantitative?
QUANTIATIVE!! tells you how much Rhogam is needed
Rhogam is also known as
passive anti-D
What does the KB test look for?
quantity of hemoglobin F in circulation of the pregnant person
What is hemoglobin F?
Hemoglobin made only by babies, up until they are around 2-4 months old
Is Kleihauer Betke Test (KB Test) done on Rh positive preggo people?
YES! it can be done on Rh positive or negative people
Why are fetal screens only performed on the Rh negative moms?
Fetal screen uses anti-D to bind to the baby’s Rh positive cells. If the mother was Rh positive, then the anti-D would bind to the mom’s Rh positive cells.
Why can the Kleihauer Betke (KB) test be performed on Rh negative AND Rh positive mothers?
KB test detects how much hemoglobin F is present which has no correlation to Rh status. Hemoglobin F is the primary hemoglobin found in babies which adults lack. As the baby gets older the hemoglobin F values decrease and the hemoglobin A (which is the predominant hemoglobin found in adults) increases.
A positive DAT in a newborn is considered a critical result. Which test can be done in chemistry to monitor the destruction of the newborn’s RBCs?
Bilirubin levels
What is the purpose of administering Rhogam to Rh negative mothers?
Rhogam is given to Rh negative mothers to prevent the mother’s immune system from making their own real anti-D. Rhogam is a PASSIVE anti-D.
A labor and delivery patient is A Negative with a history of a real anti-D. She gives birth to an O Positive baby boy. Can we give Rhogam to this patient?
This patient is NOT a candidate for rhogam!! She already made a real anti-D! If you give her Rhogam (passive anti-D) you will be increasing the level of anti-D present thereby potentially increasing the destruction of the baby’s Rh positive cells.
What can cause a false positive on a CORD specimen? How do you remedy it?
- Wharton’s jelly
- Wash CORD specimen 8x
Van Helsing has a history of an anti-Cw, but his current screen is negative. What type of crossmatch should be performed?
full crossmatch
Frankenstein needs 4 units of blood. He has an anti-e and an anti-K. How many units do you need to screen to find a unit that is negative for K and e?
Frequency of e: 98%
Frequency of K: 9%
4 units / (2%)(91%)
4/ .0182
~219.78 units screened
Dracula has an anti-K. He was transfused in Transylvania Hospital for Vampires 30 days ago. Can he be phenotyped for Kell? Why or Why Not?
No, he was transfused in the last 90 days which means he will get a mixed field reaction.
Jacob Black has an anti-c and was transfused 4 years ago. Can you phenotype him for the c antigen? Why or why not?
Yes, he was not transfused within the last 90 days. The transfusion will not effect the result.
CorpseHusband needs to be transfused. He is a B-Negative patient who has anti-C and anti-E. These are the packs currently available, which can be suitable for crossmatch?
1. O Negative unit
2. A Negative unit that is negative for C and E antigens
3. B Positive unit that is negative for C and E antigens
4. O Negative unit that is negative for C and E antigens
5. B Negative unit
6. B Negative unit that is negative for C and E antigens
- No
- No
- No
- Yes
- No
- Yes
