BB - HDFN, RhoGAM Flashcards
(39 cards)
HDFN is caused by maternal antibodies crossing the ___ to attack fetal RBCs. The maternal antibodies are in the class…
Placenta
IgG
Maternal antibodies target fetal antigens inherited from…
The father
-mother does not make antibodies against her “own” antigens
Causes of HDFN is classified into 3 different categories
Caused by anti-D hemolytic disease
Caused by antibodies against other antigens (ie anti-c, anti-K)
Caused by ABO hemolytic disease
ABO hemolytic disease is caused by these antibodies… made by a mother of this ABO type… What immunoglobulin class are they?
anti-A, anti-B or anti-A,B
-commonly anti-A,B since majority are IgG
Group O mothers
IgG
-usually, they are IgM, but in this case, they’re IgG, so they can cross the placenta
3 stages of HDFN testing
Prenatal screening
Cord blood work-up
Post partum work-up
Prenatal screening - what tests are involved for the mother?
ABORh (D)
Antibody screen
Antibody ID panel if screen is positive
Why would we want to do multiple antibody titers during pregnancy?
To determine if the titer is rising
- amniocentesis if significant titer rise
- antibody titrations on mother’s plasma
Cord blood work-up involves these tests. Should we do reverse typing?
Cord cells typed AFTER BIRTH:
ABORh (D)
DAT
No reverse typing
- baby has maternal antibodies
- baby does not produce own antibodies yet
What should we do next if the cord cells are DAT positive?
Perform an eluate from cord cells
Do an antibody ID from eluate (screens rarely done)
Post partum work-up involves these tests for the mother
ABORh (D)
Antibody screen
Antibody ID panel
Additional post partum work-up for an Rh negative mother and an Rh positive baby is this screening test… What does the test look for in maternal circulation?
Rosette Screen
Presence and amount of fetal cells
A positive Rosette screen is followed up by the ___ test. The test is useful for calculating…
Kleihauer-Betke test
The dose of Rh immune globulin to give
Why must cord blood cells be washed so much?
To remove Wharton’s Jelly
If the mother had no unexpected antibodies, what other reason could explain HDFN?
ABO hemolytic disease
When doing an antibody ID panel for both mother and baby to identify an unexpected antibody, should we use different cell numbers/lots or the same cells?
Same
What can we conclude if the same panel cells react to both mother’s serum and baby eluate?
Maternal alloantibodies attached to baby’s RBCs
The Kleihauer-Betke test utilizes this concept as a way to enable fetal RBCs to be recognized
Fetal hemoglobin (hemoglobin F) is resistant to acid elution -resistant to staining
What is the ultimate purpose of the Rosette test? A positive Rosette screening test should be followed up with…
Provide indication if bleeding was larger than normal
-test does NOT provide evidence that increased dose of RhoGAM is required to protect mother from producing anti-D; do KB test
More cumbersome Kleihauer-Betke quantitative test
-determines dose of RhoGAM to give
The Rosette test requires these components
Maternal blood -D negative mother -contains D positive fetal cells Anti-D Ficin-treated D positive RBCs
Fetal D+ RBCs will be surrounded by indicator D+ cells, making them easier to see
Rosette test - what do the positive and negative results look like?
Positive = 3 or more clumps
Negative = 2 or fewer clumps
The most clinically significant non-Rh system antibodies that cause HDFN are…
Anti-Kell
HDFN is this type of hemolysis
Extravascular
- maternal IgGs attach to antigens on fetal RBCs
- removed by macrophages in spleen
RBC hemolysis releases hemoglobin, which metabolizes to ___. Buildup causes damage to this organ…
Bilirubin
Brain
-sunbathe or put under UV light to clear bilirubin from baby
Clinically significant alloantibodies are reactive at these 2 stages of the screening test
37C
AHG
- clinically significant alloantibodies = IgG
- Rh typing/weak D
