A patient's cells give 3+ with one monoclonal IgM anti-D and 0 with a second licensed anti-D made from a different clone. Controls are valid. What is the most likely explanation?

A partial D lacking the second clone's epitope

Two red cell populations after transfusion

A positive DAT giving a false-positive result

A weak D type 1 with too few D sites

Rh antigens such as D, C and E are carried on:

Transmembrane proteins coded by RHD and RHCE

Glycophorin A and glycophorin B

GPI-anchored proteins on the cell surface

Carbohydrate chains built by glycosyltransferases

A D-negative woman's postpartum sample shows no reaction with anti-D at immediate spin but a 1+ mixed-field reaction in the weak D test. She typed D-negative in pregnancy, and her baby is D-positive. The most likely cause is:

A large fetomaternal hemorrhage

A weak D phenotype in the mother

Passive anti-D from antenatal RhIG

A partial D phenotype in the mother

How well developed is the D antigen on a newborn's red cells?

Well developed, close to adult levels

Weak, reaching adult levels in childhood

Present only on fetal reticulocytes

Absent until a few months after birth

Rh system, weak D and partial D

19 DOH Abu Dhabi (HAAD) lab licensing practice questions on Rh system, weak D and partial D, 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 · Hard
A patient's cells give 3+ with one monoclonal IgM anti-D and 0 with a second licensed anti-D made from a different clone. Controls are valid. What is the most likely explanation?
1. ATwo red cell populations after transfusion
2. BA positive DAT giving a false-positive result
3. CA partial D lacking the second clone's epitope
4. DA weak D type 1 with too few D sites
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Answer: C · A partial D lacking the second clone's epitope
Each monoclonal anti-D recognizes one D epitope. A partial D protein lacks some epitopes, so it can react strongly with one clone and not at all with another clone that targets a missing epitope. Weak D, a positive DAT or a mixed population would affect both reagents in a similar way. The patient is managed as D-negative for transfusion and RhIG, and RHD genotyping can identify the variant.
- A: A mixed population would give mixed-field reactions with both reagents.
- B: IgM reagents at immediate spin are rarely affected by a positive DAT, and the controls are valid.
- D: Weak D gives weak reactions with both reagents, not 3+ and 0.
Question 2 · Easy
Rh antigens such as D, C and E are carried on:
1. ATransmembrane proteins coded by RHD and RHCE
2. BGlycophorin A and glycophorin B
3. CGPI-anchored proteins on the cell surface
4. DCarbohydrate chains built by glycosyltransferases
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Answer: A · Transmembrane proteins coded by RHD and RHCE
RhD and RhCE are nonglycosylated proteins that cross the red cell membrane 12 times, coded by the closely linked RHD and RHCE genes on chromosome 1. They sit in a complex with the Rh-associated glycoprotein (RhAG), which is needed for their expression. Because the antigens are protein, they are well developed at birth and are found only on red cells. ABO antigens, by contrast, are carbohydrates made by transferases.
- B: Glycophorins A and B carry the MNS antigens.
- C: GPI-anchored proteins carry systems such as Cromer and Dombrock, not Rh.
- D: Carbohydrate antigens made by transferases describe ABO, H and Lewis.
Question 3 · Medium
The Fisher-Race haplotype dCe is written in Wiener notation as:
1. AR1
2. Br'
3. Cr''
4. Dry
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Answer: B · r'
In Wiener notation, R means that D is present and r means that D is absent. A single prime stands for C and a double prime for E, so dCe is r' and dcE is r''. ry is dCE, which carries both C and E, and R1 is DCe, the D-positive form of r'. Panel sheets often use these short forms, so quick conversion is a practical skill.
- A: R1 is DCe; the capital R shows that D is present.
- C: r'' is dcE: the double prime stands for E, not C.
- D: ry is dCE, which carries both C and E.
Question 4 · Hard
A D-negative woman's postpartum sample shows no reaction with anti-D at immediate spin but a 1+ mixed-field reaction in the weak D test. She typed D-negative in pregnancy, and her baby is D-positive. The most likely cause is:
1. AA weak D phenotype in the mother
2. BPassive anti-D from antenatal RhIG
3. CA large fetomaternal hemorrhage
4. DA partial D phenotype in the mother
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Answer: C · A large fetomaternal hemorrhage
D-positive fetal cells that enter the mother's circulation form a small separate population, which anti-D and antiglobulin reagent agglutinate as a mixed-field reaction. Mixed field in a postpartum weak D test therefore points to a large fetomaternal hemorrhage, not to maternal weak D. Labeling her weak D-positive would wrongly withhold RhIG. The bleed is quantified by Kleihauer-Betke or flow cytometry so that the right RhIG dose is given.
- A: Maternal weak D would give a uniform reaction, and she typed D-negative in pregnancy.
- B: RhIG is an antibody in plasma; it cannot make her own D-negative cells react with anti-D.
- D: Partial D would give a uniform reaction and was not seen on antenatal typing.
Question 5 · Easy
How well developed is the D antigen on a newborn's red cells?
1. AWell developed, close to adult levels
2. BWeak, reaching adult levels in childhood
3. CPresent only on fetal reticulocytes
4. DAbsent until a few months after birth
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Answer: A · Well developed, close to adult levels
Rh antigens can be detected early in fetal life and are well developed at birth. This is why cord blood D typing is reliable, and why maternal anti-D can destroy fetal red cells during pregnancy. A and B antigens, in contrast, are weaker at birth and reach adult strength only in early childhood. A newborn heavily coated with maternal anti-D can still type falsely D-negative, but that is a separate problem.
- B: Slow maturing over the first years of life describes A and B, not D.
- C: D is found on all red cells, not only on reticulocytes.
- D: D is present well before birth, not only after it.
Question 6 · Hard
A patient's cells are D-negative at immediate spin and 2+ in the antiglobulin (weak D) phase. The DAT is 2+ with anti-IgG. How should the weak D result be interpreted?
1. APositive, so the patient is weak D-positive
2. BInvalid, because the cells are already IgG-coated
3. CPositive, pointing to a partial D phenotype
4. DValid, provided the immediate-spin control is negative
Answer and explanation in LearnFree account
Question 7 · Hard
The newborn of a woman with anti-D (titer 512) types D-negative with an IgM monoclonal anti-D, but the DAT is 4+ with anti-IgG. What is the most likely explanation?
1. AThe baby is D-negative with ABO HDFN
2. BRh immune globulin given to the mother in pregnancy
3. CThe baby has a weak D from the father
4. DMaternal anti-D is blocking the D sites
Answer and explanation in LearnFree account
Question 8 · Medium
At the gene level, many partial D phenotypes such as DVI arise from:
1. AMissense changes in the membrane-spanning part of RhD
2. BDeletion of the whole RHD gene
3. CHybrid genes in which RHCE replaces parts of RHD
4. DInactivating mutations in the RHAG gene
Answer and explanation in LearnFree account
Question 9 · Easy
In people of African ancestry, the most common Rh haplotype is:
1. Adce (r)
2. BDCe (R1)
3. CDcE (R2)
4. DDce (R0)
Answer and explanation in LearnFree account
Question 10 · Hard
A D-negative pregnant woman's partner types D+ C+ c+ E- e+. Using common haplotype frequencies in people of European ancestry, his most probable genotype and the chance that a fetus is D-positive are:
1. ADCe/DCe (R1R1): about 100%
2. BDcE/dce (R2r): about 50%
3. CDCe/dce (R1r): about 50%
4. DDCe/Dce (R1R0): about 100%
Answer and explanation in LearnFree account
Question 11 · Hard
A first-time donor of East Asian ancestry types D-negative, including the antiglobulin (weak D) test. A D-negative recipient of her red cells later forms anti-D. The most likely explanation is:
1. AA DEL phenotype in the donor
2. BA weak D type 1 in the donor
3. CA partial D in the recipient
4. DPassive anti-D from donor plasma
Answer and explanation in LearnFree account
Question 12 · Medium
What is the usual genetic basis of the D-negative phenotype in people of European ancestry?
1. AA hybrid RHD-CE-D gene
2. BA DEL allele with very few D sites
3. CA deletion of the whole RHD gene
4. DAn inactive RHD pseudogene
Answer and explanation in LearnFree account
Question 13 · Hard
A 27-year-old woman at 11 weeks of pregnancy gives a weak (1+) D reaction with two anti-D reagents. RHD genotyping has been sent. Until the result is back, she should be managed as:
1. AD-negative, eligible for RhIG and given D-negative red cells
2. BD-positive for transfusion, but still given RhIG
3. CD-positive, needing no RhIG and given D-positive red cells
4. DUndecided, with RhIG chosen only after delivery
Answer and explanation in LearnFree account
Question 14 · Medium
A man with the genotype Dce/dCe shows weaker D reactions than his sister, who is Dce/dce. This position effect is caused by:
1. AA partial D allele from one parent
2. BC carried on the haplotype opposite to D
3. CLoss of RHCE on one chromosome
4. DA regulator gene lowering all Rh antigens
Answer and explanation in LearnFree account
Question 15 · Hard
A 33-year-old woman of African ancestry, with three previous pregnancies and no transfusions, has a positive antibody screen before elective gallbladder surgery. On the antiglobulin-phase panel, every e-positive cell (R1R1, R1r, R0r and rr) reacts 2+, and both R2R2 cells, which lack e, are nonreactive. Antibodies to K, Duffy, Kidd and MNS antigens are excluded. The autocontrol and DAT are negative, and there is no hemolysis: hemoglobin 124 g/L (12.4 g/dL), bilirubin 9 µmol/L (0.5 mg/dL). Her red cells type D+ C- c+ E- e+ with two different anti-e reagents. The best interpretation is:
1. AAn e typing error; her cells lack e
2. BAlloanti-e from a partial e phenotype
3. CWarm autoantibody with e specificity
4. DAnti-f to the compound ce antigen
Answer and explanation in LearnFree account
Question 16 · Hard
A 31-year-old woman, whose parents are first cousins, is 22 weeks pregnant with her third child; her second baby needed an exchange transfusion for HDFN. She has never been transfused. Her red cells give unusually strong reactions with anti-D and type C-, c-, E- and e- with reagents whose controls are valid. Her antibody screen and an 11-cell panel, which includes R1R1, R2R2 and rr cells, react 3+ with every cell at the antiglobulin phase and 4+ with ficin-treated cells. The autocontrol and DAT are negative, and her hemoglobin is 112 g/L (11.2 g/dL). Which red cells would be compatible if she needs transfusion?
1. Arr (dce/dce) units, which lack D
2. BR1R1 (DCe/DCe) units, which lack c and E
3. CRzRz (DCE/DCE) units, which lack c and e
4. DD-- or Rhnull units from a rare donor panel
Answer and explanation in LearnFree account
Question 17 · Hard
Five first-time blood donors are D-typed, including the weak D test, as shown. The donors whose D type cannot yet be reported are:
Figure: MedExams
1. ADonor 4 only
2. BDonor 5 only
3. CDonors 4 and 5
4. DDonors 3 and 4
Answer and explanation in LearnFree account
Question 18 · Medium
A donor's red cells are D-negative at immediate spin but D-positive at the antiglobulin phase (weak D). How should the donor unit be labeled?
1. AD-negative
2. BD-positive
3. CIt should be discarded
4. DUntyped
Answer and explanation in LearnFree account
Question 19 · Medium
Why is a control needed with some anti-D reagents?
1. ATo confirm the patient's ABO group
2. BTo check the centrifuge speed and time
3. CTo detect false positives, such as DAT-positive cells
4. DTo measure the strength of the anti-A and anti-B reagents
Answer and explanation in LearnFree account

Rh system, weak D and partial D

A patient's cells give 3+ with one monoclonal IgM anti-D and 0 with a second licensed anti-D made from a different clone. Controls are valid. What is the most likely explanation?

Rh antigens such as D, C and E are carried on:

The Fisher-Race haplotype dCe is written in Wiener notation as:

A D-negative woman's postpartum sample shows no reaction with anti-D at immediate spin but a 1+ mixed-field reaction in the weak D test. She typed D-negative in pregnancy, and her baby is D-positive. The most likely cause is:

How well developed is the D antigen on a newborn's red cells?

A patient's cells are D-negative at immediate spin and 2+ in the antiglobulin (weak D) phase. The DAT is 2+ with anti-IgG. How should the weak D result be interpreted?

The newborn of a woman with anti-D (titer 512) types D-negative with an IgM monoclonal anti-D, but the DAT is 4+ with anti-IgG. What is the most likely explanation?

At the gene level, many partial D phenotypes such as DVI arise from:

In people of African ancestry, the most common Rh haplotype is:

A D-negative pregnant woman's partner types D+ C+ c+ E- e+. Using common haplotype frequencies in people of European ancestry, his most probable genotype and the chance that a fetus is D-positive are:

A first-time donor of East Asian ancestry types D-negative, including the antiglobulin (weak D) test. A D-negative recipient of her red cells later forms anti-D. The most likely explanation is:

What is the usual genetic basis of the D-negative phenotype in people of European ancestry?

A 27-year-old woman at 11 weeks of pregnancy gives a weak (1+) D reaction with two anti-D reagents. RHD genotyping has been sent. Until the result is back, she should be managed as:

A man with the genotype Dce/dCe shows weaker D reactions than his sister, who is Dce/dce. This position effect is caused by:

Five first-time blood donors are D-typed, including the weak D test, as shown. The donors whose D type cannot yet be reported are:

A donor's red cells are D-negative at immediate spin but D-positive at the antiglobulin phase (weak D). How should the donor unit be labeled?

Why is a control needed with some anti-D reagents?