In a Kleihauer-Betke test, why do fetal red cells stay stained while the mother's cells appear as pale ghosts?

Hb F resists elution in acid buffer

Fetal cells are larger and take up more stain

Hb A resists elution in acid buffer

The alcohol fixative lyses adult red cells

For an exchange transfusion in a newborn with anti-D HDFN, the crossmatch is preferably done with:

An eluate from the infant's cells

A woman whose last baby needed intrauterine transfusions for anti-D HDFN is now 16 weeks pregnant. Her anti-D titer is 8, and her partner is homozygous for RHD. What is the best plan?

Middle cerebral artery Doppler, whatever the titer

Monthly titers, with Doppler once the titer is 32

No extra monitoring while the titer stays below 16

Rh immune globulin to keep the titer from rising

A pregnant woman has anti-K. Her partner types K-negative, and paternity is certain. What is the risk to the fetus from this antibody?

Very low, because the fetus should be K-negative

Moderate, so Doppler monitoring should start now

Unknown until the anti-K titer is measured

High, because anti-K suppresses fetal erythropoiesis

Hemolytic disease of the fetus and newborn

19 DOH Abu Dhabi (HAAD) lab licensing practice questions on Hemolytic disease of the fetus and newborn, part of Blood Banking. The first 19 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
In a Kleihauer-Betke test, why do fetal red cells stay stained while the mother's cells appear as pale ghosts?
1. AHb F resists elution in acid buffer
2. BFetal cells are larger and take up more stain
3. CHb A resists elution in acid buffer
4. DThe alcohol fixative lyses adult red cells
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Answer: A · Hb F resists elution in acid buffer
The fixed smear is placed in an acid citrate-phosphate buffer, which washes adult hemoglobin out of the cells. Fetal hemoglobin resists acid elution, so fetal cells keep their hemoglobin and stain pink with the counterstain, while adult cells look like empty ghosts. The percentage of fetal cells is counted and converted to a bleed volume. Maternal cells with raised Hb F, as in some hemoglobin disorders, can make the test overestimate the bleed.
- B: Fetal cells are larger, but staining depends on retained Hb F, not on size.
- C: It is the other way round: Hb A is eluted by the acid.
- D: The fixative preserves both cell types; the acid buffer removes the Hb A.
Question 2 · Medium
For an exchange transfusion in a newborn with anti-D HDFN, the crossmatch is preferably done with:
1. APooled normal adult plasma
2. BAn eluate from the infant's cells
3. CThe infant's cord serum
4. DThe mother's plasma
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Answer: D · The mother's plasma
The antibody in the baby came from the mother, and her plasma usually holds it at a higher level, so it gives the most sensitive crossmatch. The donor red cells are group O, or ABO compatible with both mother and baby, and lack the antigen of the maternal antibody. If no maternal sample is available, the infant's plasma or an eluate from the infant's cells can be used instead. The mother's sample also makes it easier to confirm the antibody's specificity.
- A: Normal plasma does not contain the maternal antibody.
- B: An eluate can be used if no maternal sample is available, but it is not the first choice.
- C: Cord serum has less antibody than the mother's plasma, so it is less sensitive.
Question 3 · Easy
In saline tube antiglobulin titration, many laboratories set the critical anti-D titer, at which the fetus starts to be monitored for anemia, at:
1. A128 to 256
2. B2 to 4
3. C1,024 or higher
4. D16 to 32
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Answer: D · 16 to 32
The critical titer is the level below which severe HDFN from anti-D is very unlikely. With the saline tube antiglobulin method, most centers use 16 or 32, and each laboratory sets its own value for its method. Once the titer reaches that level, the fetus is followed with middle cerebral artery Doppler. Gel and other sensitive methods give higher titers, so the cut-off must match the method used.
- A: 128 to 256 is far above the usual trigger; monitoring starts well before this.
- B: Titers of 2 to 4 rarely go with fetal anemia from anti-D.
- C: Waiting for a titer of 1,024 would miss many fetuses at risk.
Question 4 · Hard
A woman whose last baby needed intrauterine transfusions for anti-D HDFN is now 16 weeks pregnant. Her anti-D titer is 8, and her partner is homozygous for RHD. What is the best plan?
1. AMonthly titers, with Doppler once the titer is 32
2. BNo extra monitoring while the titer stays below 16
3. CMiddle cerebral artery Doppler, whatever the titer
4. DRh immune globulin to keep the titer from rising
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Answer: C · Middle cerebral artery Doppler, whatever the titer
After a previously affected pregnancy, the maternal titer no longer predicts fetal risk: severe anemia can occur below the usual critical titer, and the disease tends to start earlier and be worse each time. The fetus is therefore followed by middle cerebral artery peak systolic velocity from about 16 to 18 weeks, without waiting for a titer trigger. With a homozygous partner every baby will be D-positive, so fetal RHD testing adds nothing. Rh immune globulin has no role in a woman who is already immunized.
- A: After an affected pregnancy the titer does not predict risk, so waiting for 32 is unsafe.
- B: Severe fetal anemia can occur below the usual critical titer in this setting.
- D: Rh immune globulin does not lower an anti-D that she already makes.
Question 5 · Medium
A pregnant woman has anti-K. Her partner types K-negative, and paternity is certain. What is the risk to the fetus from this antibody?
1. AVery low, because the fetus should be K-negative
2. BModerate, so Doppler monitoring should start now
3. CUnknown until the anti-K titer is measured
4. DHigh, because anti-K suppresses fetal erythropoiesis
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Answer: A · Very low, because the fetus should be K-negative
A fetus is at risk only if it inherits the antigen, and here the antigen could come only from the father. If the partner is K-negative (kk) and paternity is certain, the fetus will be K-negative and cannot be harmed by anti-K. Most anti-K in pregnancy follows an earlier transfusion, so this situation is common. If paternity is uncertain or the partner is K-positive, fetal K genotyping and close monitoring are needed, because anti-K can cause severe anemia even at low titers.
- B: Doppler monitoring is for a fetus that may carry the antigen.
- C: The titer does not matter if the fetus cannot carry the antigen.
- D: Anti-K can suppress fetal erythropoiesis, but only in a K-positive fetus.
Question 6 · Hard
A D-negative mother's Kleihauer-Betke test after delivery shows 18 fetal cells among 2,000 red cells counted. With her blood volume taken as 5,000 mL, the estimated fetal bleed is about:
1. A90 mL of fetal whole blood
2. B22.5 mL of fetal whole blood
3. C4.5 mL of fetal whole blood
4. D45 mL of fetal whole blood
Answer and explanation in LearnFree account
Question 7 · Medium
In the rosette screening test for fetomaternal hemorrhage, the maternal sample is incubated with anti-D, washed, and then mixed with indicator cells that are:
1. AIgG-coated check cells
2. BThe baby's own cord red cells
3. CD-positive reagent red cells
4. DD-negative reagent red cells
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Question 8 · Hard
A D-negative mother has anti-D with a titer of 512. Her anemic, jaundiced newborn's cord cells type D-negative with an IgM monoclonal anti-D, but the DAT is 4+ with anti-IgG. The most likely reason for the D-negative result is:
1. AThe baby is truly D-negative
2. BMaternal anti-D is blocking the D sites
3. CWharton's jelly is coating the cord cells
4. DThe baby carries a partial D antigen
Answer and explanation in LearnFree account
Question 9 · Medium
At 28 weeks, a D-negative woman who has never received Rh immune globulin has anti-D with a titer of 64. Should antenatal Rh immune globulin be given?
1. AYes; it will lower her own anti-D titer
2. BYes; it protects her next pregnancy
3. CNo; she is already immunized, so it gives no benefit
4. DYes, but a double dose is needed at this titer
Answer and explanation in LearnFree account
Question 10 · Easy
After a D-negative woman delivers a D-positive baby, postpartum Rh immune globulin should be given within:
1. A14 days of delivery
2. B7 days of delivery
3. C24 hours of delivery
4. D72 hours of delivery
Answer and explanation in LearnFree account
Question 11 · Hard
A woman's D type was recorded as negative by direct agglutination. After she delivers a D-positive baby, her rosette test shows rosettes in every field, yet a Kleihauer-Betke test shows only 0.1% fetal cells. The most likely explanation is:
1. AA massive fetomaternal hemorrhage
2. BThe mother has a weak D phenotype
3. CAntenatal Rh immune globulin in her plasma
4. DThe baby has a weak D phenotype
Answer and explanation in LearnFree account
Question 12 · Medium
At her first antenatal visit, a D-positive woman has an antibody screen. Why is this test done even though she is D-positive?
1. AHer plasma must be checked for passive anti-D
2. BIt predicts the ABO group of the baby
3. CAnti-c, anti-E and anti-K can still cause HDFN
4. DIt decides whether she needs Rh immune globulin
Answer and explanation in LearnFree account
Question 13 · Hard
A D-negative woman weighing 80 kg has a Kleihauer-Betke result of 0.6% fetal cells. The laboratory takes blood volume as 70 mL/kg and gives one 300 µg vial per 30 mL of fetal whole blood, rounded to the nearest whole number, plus one extra vial. The dose is:
1. A4 vials
2. B3 vials
3. C1 vial
4. D2 vials
Answer and explanation in LearnFree account
Question 14 · Easy
For a D-negative mother, which cord blood result decides whether she needs postpartum Rh immune globulin?
1. AThe infant's D type
2. BThe infant's hemoglobin level
3. CThe infant's bilirubin level
4. DThe infant's ABO group
Answer and explanation in LearnFree account
Question 15 · Hard
A 30-year-old D-positive (R1R1) woman in her third pregnancy has anti-c, found at booking. At 16 weeks a referral laboratory reported an anti-c titer of 8 by the saline tube antiglobulin method, and part of that sample was kept frozen. At 24 weeks she moves to a new hospital, whose laboratory measures the titer by a gel column antiglobulin method and gets 64. Her partner types c-positive. The obstetric team uses a critical titer of 16, set with the tube method. Before a rise in titer is reported, what should the laboratory do?
1. AReport a three-dilution rise since 16 weeks
2. BRepeat the gel titer alone in two weeks
3. CDivide the gel titer by four to convert it
4. DRetest both samples side by side by one method
Answer and explanation in LearnFree account
Question 16 · Hard
A 29-year-old D-negative woman with known beta-thalassemia trait delivers a D-positive baby in an Abu Dhabi hospital, and her rosette test is positive. The Kleihauer-Betke slide is hard to read because many maternal cells stain pink, so flow cytometry is done with anti-HbF and anti-carbonic anhydrase: HbF-positive, carbonic anhydrase-negative cells 0.45%; HbF-positive, carbonic anhydrase-positive cells 1.80%. Take her blood volume as 5,000 mL. The laboratory gives one 300 µg vial of Rh immune globulin per 30 mL of fetal whole blood, rounds up at 0.5 or more and down below 0.5, then adds one vial. The number of vials needed is:
1. A3 vials
2. B1 vial
3. C2 vials
4. D5 vials
Answer and explanation in LearnFree account
Question 17 · Medium
A D-negative woman with anti-D from a previous pregnancy has the titrations shown. The laboratory's critical titer is 16. The 28-week titer and its meaning are:
Figure: MedExams
1. A32: a fourfold rise to above the critical titer
2. B64: an eightfold rise above the critical titer
3. C32: within the variation of the method
4. D16: a twofold rise to the critical titer
Answer and explanation in LearnFree account
Question 18 · Hard
Besides anti-D and anti-c, which antibody is an important cause of severe HDFN, partly by suppressing fetal red cell production?
1. AAnti-I
2. BAnti-Lea
3. CAnti-K
4. DAnti-M
Answer and explanation in LearnFree account
Question 19 · Hard
A group A newborn of a group O mother develops jaundice in the first day. The DAT is weakly positive and spherocytes are seen. What is the most likely cause?
1. AG6PD deficiency
2. BPhysiological jaundice
3. CABO hemolytic disease of the newborn
4. DAnti-D hemolytic disease of the newborn
Answer and explanation in LearnFree account

Hemolytic disease of the fetus and newborn

In a Kleihauer-Betke test, why do fetal red cells stay stained while the mother's cells appear as pale ghosts?

For an exchange transfusion in a newborn with anti-D HDFN, the crossmatch is preferably done with:

In saline tube antiglobulin titration, many laboratories set the critical anti-D titer, at which the fetus starts to be monitored for anemia, at:

A woman whose last baby needed intrauterine transfusions for anti-D HDFN is now 16 weeks pregnant. Her anti-D titer is 8, and her partner is homozygous for RHD. What is the best plan?

A pregnant woman has anti-K. Her partner types K-negative, and paternity is certain. What is the risk to the fetus from this antibody?

A D-negative mother's Kleihauer-Betke test after delivery shows 18 fetal cells among 2,000 red cells counted. With her blood volume taken as 5,000 mL, the estimated fetal bleed is about:

In the rosette screening test for fetomaternal hemorrhage, the maternal sample is incubated with anti-D, washed, and then mixed with indicator cells that are:

A D-negative mother has anti-D with a titer of 512. Her anemic, jaundiced newborn's cord cells type D-negative with an IgM monoclonal anti-D, but the DAT is 4+ with anti-IgG. The most likely reason for the D-negative result is:

At 28 weeks, a D-negative woman who has never received Rh immune globulin has anti-D with a titer of 64. Should antenatal Rh immune globulin be given?

After a D-negative woman delivers a D-positive baby, postpartum Rh immune globulin should be given within:

A woman's D type was recorded as negative by direct agglutination. After she delivers a D-positive baby, her rosette test shows rosettes in every field, yet a Kleihauer-Betke test shows only 0.1% fetal cells. The most likely explanation is:

At her first antenatal visit, a D-positive woman has an antibody screen. Why is this test done even though she is D-positive?

A D-negative woman weighing 80 kg has a Kleihauer-Betke result of 0.6% fetal cells. The laboratory takes blood volume as 70 mL/kg and gives one 300 µg vial per 30 mL of fetal whole blood, rounded to the nearest whole number, plus one extra vial. The dose is:

For a D-negative mother, which cord blood result decides whether she needs postpartum Rh immune globulin?

A D-negative woman with anti-D from a previous pregnancy has the titrations shown. The laboratory's critical titer is 16. The 28-week titer and its meaning are:

Besides anti-D and anti-c, which antibody is an important cause of severe HDFN, partly by suppressing fetal red cell production?

A group A newborn of a group O mother develops jaundice in the first day. The DAT is weakly positive and spherocytes are seen. What is the most likely cause?