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CLS 790 > BB - HDFN, RhoGAM > Flashcards

BB - HDFN, RhoGAM Flashcards

1
Q

HDFN is caused by maternal antibodies crossing the ___ to attack fetal RBCs. The maternal antibodies are in the class…

A

Placenta

IgG

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2
Q

Maternal antibodies target fetal antigens inherited from…

A

The father

-mother does not make antibodies against her “own” antigens

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3
Q

Causes of HDFN is classified into 3 different categories

A

Caused by anti-D hemolytic disease

Caused by antibodies against other antigens (ie anti-c, anti-K)

Caused by ABO hemolytic disease

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4
Q

ABO hemolytic disease is caused by these antibodies… made by a mother of this ABO type… What immunoglobulin class are they?

A

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

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5
Q

3 stages of HDFN testing

A

Prenatal screening

Cord blood work-up

Post partum work-up

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6
Q

Prenatal screening - what tests are involved for the mother?

A

ABORh (D)
Antibody screen
Antibody ID panel if screen is positive

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7
Q

Why would we want to do multiple antibody titers during pregnancy?

A

To determine if the titer is rising

  • amniocentesis if significant titer rise
  • antibody titrations on mother’s plasma
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8
Q

Cord blood work-up involves these tests. Should we do reverse typing?

A

Cord cells typed AFTER BIRTH:
ABORh (D)
DAT

No reverse typing

  • baby has maternal antibodies
  • baby does not produce own antibodies yet
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9
Q

What should we do next if the cord cells are DAT positive?

A

Perform an eluate from cord cells

Do an antibody ID from eluate (screens rarely done)

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10
Q

Post partum work-up involves these tests for the mother

A

ABORh (D)
Antibody screen
Antibody ID panel

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11
Q

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?

A

Rosette Screen

Presence and amount of fetal cells

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12
Q

A positive Rosette screen is followed up by the ___ test. The test is useful for calculating…

A

Kleihauer-Betke test

The dose of Rh immune globulin to give

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13
Q

Why must cord blood cells be washed so much?

A

To remove Wharton’s Jelly

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14
Q

If the mother had no unexpected antibodies, what other reason could explain HDFN?

A

ABO hemolytic disease

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15
Q

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?

A

Same

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16
Q

What can we conclude if the same panel cells react to both mother’s serum and baby eluate?

A

Maternal alloantibodies attached to baby’s RBCs

17
Q

The Kleihauer-Betke test utilizes this concept as a way to enable fetal RBCs to be recognized

A 
Fetal hemoglobin (hemoglobin F) is resistant to acid elution
-resistant to staining
18
Q

What is the ultimate purpose of the Rosette test? A positive Rosette screening test should be followed up with…

A

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

19
Q

The Rosette test requires these components

A 
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

20
Q

Rosette test - what do the positive and negative results look like?

A

Positive = 3 or more clumps

Negative = 2 or fewer clumps

21
Q

The most clinically significant non-Rh system antibodies that cause HDFN are…

A

Anti-Kell

22
Q

HDFN is this type of hemolysis

A

Extravascular

  • maternal IgGs attach to antigens on fetal RBCs
  • removed by macrophages in spleen
23
Q

RBC hemolysis releases hemoglobin, which metabolizes to ___. Buildup causes damage to this organ…

A

Bilirubin

Brain
-sunbathe or put under UV light to clear bilirubin from baby

24
Q

Clinically significant alloantibodies are reactive at these 2 stages of the screening test

A

37C

AHG

  • clinically significant alloantibodies = IgG
  • Rh typing/weak D
25
Q

At what stage of pregnancy is RhoGAM given prophylactically? Postpartum?

A

28 weeks

Within 72 hours

26
Q

If mother is already making anti-D, what test can we perform to determine if it’s from an active or passive immunization?

A

Titration

  • titer >= 4 is active
  • titer < 4 is passive
27
Q

Clinically significant titer levels

A

16-32

28
Q

When a baby has a positive DAT, can we determine the Rh typing? Why or why not? What other testing can we do?

A

No

Baby’s RBCs are covered with mother’s antibodies. Might give false negative

Eluate

29
Q

What is the KB test calculation to determine the total volume of fetomaternal hemorrhage?

A

(# fetal cells * maternal blood volume) / # maternal cells = volume of fetal whole blood (in ml)

30
Q

The standard 300 ug dose of RhoGAM is sufficient to suppress Rh immunization of how much fetal blood?

A

15 ml fetal RBCs (30 ml whole blood)

31
Q

If 15 ml of fetal whole blood was calculated in the KB test, how many vials of RhoGAM should be given?

A

15 ml / 30 ml = 0.5
Round up to 1
Give an additional vial
Total vials = 2

1 vial of RhoGAM covers 30 ml of fetal whole blood

32
Q

ABO HDFN - O mothers almost always target fetus with type…

A

A or B

  • A in white population
  • B in black population
33
Q

Assuming an elution has been performed correctly and antibodies have been removed from cells, the antibody screen using the last wash should be ___, while the antibody screen using the eluate should be ___. Which one serves as the control?

A

Negative

Positive

Last wash serves as the control

34
Q

To do an ABO HDN test, we must use these 3 test cells… The antibodies are from this source…

A

A1, B and O cells

Eluate
-include a set of last wash control tubes as well

35
Q

Antibodies can be eluted from RBCs using these methods (3)…

A

Heat

Organic solvents

High/low pH

36
Q

Should potentiators like LISS or bovine albumin be added to the eluate?

A

No, eluate already a low ionic substrate

37
Q

What does a positive final wash screen indicate?

A

Insufficient washing when preparing the eluate

  • antibodies present in eluate may be from free antibodies in serum
  • redo eluate procedure
38
Q

The goal of an intrauterine transfusion is to maintain a hemoglobin level above… Why would we want to avoid continuous intrauterine transfusions?

A

10 g/dL

Suppresses fetus’s bone marrow production of RBCs
-stop at 34 weeks

39
Q

High levels of bilirubin in newborns can be removed through this transfusion…

A

Exchange transfusion

-removes some maternal antibodies, sensitized RBCs

CLS 790 (13 decks)

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