MLT GlobeBlood Banking: ABO system
116 Blood Banking MCQs on ABO system with answers and explanations.
Which statement about the ABO blood group system is correct?
Group O red cells lack A and B antigens, and the plasma carries naturally occurring anti-A and anti-B. Group AB has neither antibody and is the universal red-cell recipient.
Which ABO/RhD type can receive red cells of any ABO/RhD type in an emergency, since it lacks anti-A, anti-B and anti-D?
AB RhD-positive recipients have no anti-A or anti-B and their red cells carry D, so they are called universal recipients. O RhD negative is the universal red cell donor.
A person with blood group B normally has which antibody in plasma?
People make naturally occurring antibodies against the ABO antigen they lack; group B lacks A antigen and has anti-A. Group O has both anti-A and anti-B.
In ABO typing, what does reverse (serum) grouping detect?
Reverse grouping tests patient plasma against known A1 and B cells to detect antibodies, confirming forward grouping, which detects antigens on red cells.
A patient grouped as AB has which naturally occurring ABO antibodies in plasma?
People lack antibodies to their own antigens. Group AB carries both antigens, so no anti-A or anti-B is formed, which is why AB plasma is the universal plasma donor.
Which naturally occurring antibodies are expected in the plasma of a group O adult?
Group O red cells lack A and B antigens, so the plasma contains both anti-A and anti-B (plus anti-A,B), in keeping with Landsteiner's rule.
Which set of carbohydrate antigens belongs to the ABO (with H) system?
Group O cells carry unconverted H substance; there is no 'O antigen'. H is the precursor that the A and B transferases modify.
Forward typing shows no agglutination with either anti-A or anti-B reagent. The ABO group is:
Absence of both A and B antigens on red cells defines group O; AB cells would react with both reagents.
By international convention, monoclonal anti-A typing reagent is coloured:
Anti-A is tinted blue and anti-B yellow (acriflavine) so they cannot be confused; anti-D and anti-A,B are usually colourless.
Why were group AB individuals classically called universal recipients for red cells?
With no ABO antibodies, AB patients can receive red cells of any ABO group. Group O cells lacking A and B antigens make O the universal red-cell donor.
A group AB person's red cells and plasma contain which ABO components?
AB cells express both antigens; according to Landsteiner's rule the plasma lacks the corresponding antibodies.
In forward (cell) ABO grouping, what is tested against the known anti-A and anti-B reagents?
Forward grouping identifies antigens on the patient's red cells with known antisera; reverse grouping tests the patient's serum against known reagent cells.
In reverse grouping, a patient's serum agglutinates B reagent cells but not A1 cells. The patient's ABO group is:
Serum containing anti-B but no anti-A belongs to group A. Group O serum would agglutinate both cell types.
A patient's serum contains anti-B but no anti-A, and the cells react with anti-A only. The ABO group is:
Cells with A antigen and serum with anti-B only are group A. Anti-B alone is not diagnostic because group O plasma also contains it, hence both tests.
Before routine platelet transfusion, which pretransfusion step is normally performed?
Platelets are given ABO-compatible where possible and RhD-matched for girls and women; no crossmatch is needed because few red cells are present.
Reverse (serum) ABO grouping uses which patient specimen?
Reverse grouping detects anti-A and anti-B in the patient's serum or plasma using A1 and B reagent cells.
A child inherits an A allele from the mother and an O allele from the father. The child's phenotype is:
The O allele produces no functional transferase, so genotype AO expresses only A antigen.
Why is only forward (cell) typing routinely done for ABO grouping of a newborn?
Infants begin producing their own ABO antibodies at about 3 to 6 months. Any antibodies present at birth come from the mother across the placenta, so reverse typing would not reflect the baby's group.
Which plasma group can be given to patients of any ABO group?
Group AB plasma has neither anti-A nor anti-B, so it will not attack any recipient's red cells. For red cells the rule is reversed: group O is the universal donor.
The genes that encode the ABO glycosyltransferases are located on which chromosome?
The ABO gene is on chromosome 9q34. Chromosome 1 carries the RH genes, and chromosome 19 carries the H (FUT1), Se (FUT2) and Le (FUT3) genes.