Quiz 3 Flashcards
(79 cards)
Why do we do prenatal type and screens?
- To ID clinically significant Abs in mom (that can cross the placenta)
- To determine mom’s need for RhIG (Rh neg moms)
- To ID a potential ABO HDFN situation
What kind of Abs do we titer in a pregnant woman?
Abs that react at 37C (IgG)
What are the basic steps of an Ab titer?
- Make a serial dilution with the pt plasma
- React plasma with reagent cells containing Ag for corresponding Ab
- Read agglutination reaction from highest dilution to lowest
How often do we titer pregnant women with significant Abs?
Every month until the end of the 2nd trimester and every couple of weeks throughout the 3rd trimester.
What kind of reagent cells do we use for a titer on a pregnant woman?
Homozygous or heterozygous as long as it’s consistent throughout the pregnancy
What is the end-point of an Ab titer?
The highest dilution showing a 1+ reaction
What are critical titer results?
- Anti-D >/= 16
- Anti-K >/= 8
- Any other IgG Ab >/= 16
- A two tube rise in titer (ex. 1:2 - 1:8)
Why does anti-K have a lower critical titer than anti-D?
- K develops sooner in gestational age than D
- K is expressed on nRBCs and mature RBCs, where D is only expressed on mature RBCs
- Anti-K is more efficient at crossing the placenta
- Anemia caused by anti-K can be more severe earlier in gestation with a lower titer
How should you run titers to avoid subjectivity?
In parallel (last month’s sample and present sample), reading from highest titer to lowest titer
What might a physician do once the critical threshold is reached for an Ab titer?
They might begin monitoring the fetal anemia with Doppler US.
What tests are required before an exchange transfusion or intrauterine transfusion?
- Type and screen, Ab ID, and crossmatch
- Do type and screen on baby if you can for an exchange transfusion
What type of blood is used for an exchange or intrauterine transfusion? What are the special requirements?
- O neg
- Freshest available (collected within 7 days)
- CMV neg
- Hbg S neg
- Leuk reduced (for febrile reactions)
- Irradiated (for GVHD)
- Washed (to remove extra volume)
- Ag negative for mom’s Abs
What additional prep needs to be done before an exchange transfusion? Why?
- AB plasma is added to O neg blood
- To replace the entire whole blood volume
What tests are done routinely on cord blood?
Forward type and DAT
What is the purpose of doing cord blood testing?
- To determine of mom needs postpartum RhIG (Rh neg mom and Rh pos baby)
- To determine if baby’s cells are coated with an allo-Ab
What reagent is used for cold blood DAT?
Monoclonal IgG
When is ABO HDFN most likely to occur? Why?
When the mom is type O, because mom will have a higher titer of anti-A and anti-B Abs.
What will the baby’s DAT result be after ABO HDFN occurs?
It could be DAT pos or neg
What is done next if a baby has a positive DAT after ABO HDFN?
1st - ABO IAT testing using cord serum and screening cells
2nd - an elution can be done to see what Ab is coating the baby’s cells
What basic tests need to be done before a neonatal transfusion (non HDFN)?
Forward type and Ab screen on baby’s sample
If mom has an Ab, what extra steps need to be done before a neonatal transfusion (non HDFN)?
The type and screen still need to be done on the baby and an Ab ID and crossmatch can be done with mom’s sample.
If mom has a history of clinically significant Ab that is not showing up, how should blood be chosen for a neonatal transfusion?
The blood should be negative for the antigen corresponding to mom’s Abs.
When should RhIG be given?
- At 28 weeks for Rh neg moms
- In the case of a traumatic event or an invasive procedure
- If the baby is born in breech position
- In the case of vaginal bleeding
- Postpartum if the baby is Rh pos
If a mom screens positive for anti-D, they can not be given RhIG. T or F?
True
