MLT GlobeBlood Banking: Rh system – page 3
79 Blood Banking MCQs on Rh system with answers and explanations.
A D-negative woman has a spontaneous abortion at 9 weeks, and RhIG is to be given. Which dose is sufficient?
Before 12–13 weeks the fetal blood volume is small, so a 50 µg microdose is sufficient (a 300 µg dose is used where the microdose is unavailable). From the second trimester, the full 300 µg dose is used. Some current guidance (e.g. ACOG 2024) allows RhIG to be omitted before 12 weeks.
The Kleihauer-Betke test is based on the fact that fetal hemoglobin:
In acid buffer, adult hemoglobin leaches out, leaving ghost cells, while HbF-containing fetal cells stay pink after staining.
A never-transfused, never-pregnant man has a weak anti-E found only with enzyme-treated cells. This is best described as:
Anti-E is the Rh antibody most often found without a known stimulus and is often enzyme-only. RhIG contains anti-D, not anti-E.
The D type of a newborn of a D-negative mother is tested with a method that detects weak D. The purpose is to:
A weak D baby can immunize a D-negative mother, so weak D is tested to decide on postpartum RhIG.
The DEL phenotype, which types D-negative by routine methods, is most common in people of:
DEL is found in a large share of apparently D-negative East Asians. Most D-negative Europeans have a full RHD deletion instead.
At booking, a D-negative woman who has never received RhIG has anti-D with a titer of 64. Regarding RhIG, the correct action is:
RhIG prevents primary immunization but cannot reverse it. A high titer with no RhIG history means immune anti-D, which needs HDFN monitoring instead.
Immune anti-D is mainly of which IgG subclasses?
Anti-D is mostly IgG1 and IgG3, which bind Fc receptors on macrophages well, causing extravascular hemolysis.
In people of European descent, the most common Rh haplotype is:
R1 is found in about 42% of European haplotypes, followed by r (about 37%). R0 is most common in people of African descent.
A donor of European descent types D+, C+, c+, E+, e+. The most probable genotype is:
All four genotypes give this phenotype, but R1 and R2 are the most common D-positive haplotypes, so R1R2 is by far the most probable.
Red cells react very strongly with anti-D but not with anti-C, anti-c, anti-E or anti-e. This phenotype is:
D−− cells lack CcEe and show exalted D. Immunized people make anti-Hr0 and need D−− blood. Rhnull cells lack D as well.
A group O mother received antenatal RhIG at 28 weeks. Her group O, D-positive baby has a weakly positive DAT with anti-IgG and no hemolysis. The most likely cause is:
IgG anti-D from antenatal RhIG can cross the placenta and weakly coat D-positive fetal cells. ABO HDFN is excluded because mother and baby are both group O.
Intravenous anti-D immunoglobulin used to treat immune thrombocytopenia is effective only in patients who are:
Anti-D coats the patient's own D-positive red cells, which then occupy splenic Fc receptors and spare platelets. It has no target in D-negative patients.
A D-negative woman delivered a D-positive baby 5 days ago but did not receive RhIG. What is recommended?
RhIG is best given within 72 hours, but if missed it should still be given as soon as possible, since some protection may occur up to 28 days.
Many monoclonal anti-D reagents are a blend of IgM and IgG. The IgG component is included to:
IgM gives direct agglutination at immediate spin; the IgG part allows the weak D test at the antiglobulin phase.
Weak D testing is not required for transfusion recipients. A recipient with weak D whose D test is negative at immediate spin will:
Such patients are simply treated as D-negative, which is safe. Weak D testing is required for donors and for newborns of D-negative mothers.
In Fisher-Race notation, the letter 'd' means:
'd' only shows that D is absent. No d antigen or anti-d has ever been found.
Rh antigens are encoded by which genes?
RHD codes for the D protein and RHCE codes for the C/c and E/e antigens. Both are on chromosome 1. The three-gene idea of Fisher-Race is historical.
In D typing with a high-protein anti-D reagent, the Rh control tube shows agglutination. The D result is:
A positive control means something other than anti-D (for example IgG-coated cells or rouleaux) is causing agglutination, so the D result cannot be interpreted.
Absence of which blood group system proteins (null phenotype) causes stomatocytosis and a fragile red cell membrane?
Rh proteins form a membrane complex with RhAG; Rhnull cells are stomatocytic with shortened survival.
How should a patient with partial D be managed as a transfusion recipient?
Partial D lacks some D epitopes and can make anti-D, so is treated as D-negative. Most weak D types 1–3 can receive D-positive cells.