, Question 1
A patient with a historical anti-Jk^a and a current antibody screen that is
negative by gel but positive by polyethylene glycol (PEG) tube method
demonstrates a mixed-field reaction in the antihuman globulin phase. Which of
the following best explains this discrepancy?
A. Kidd antibodies are classically complement-binding and may be
undetectable by gel due to complement interference, while PEG enhances
IgM detection.
B. Gel columns can produce false-negative results for Kidd antibodies
due to their low avidity and dosage effect, whereas PEG tube testing
enhances IgG detection.
C. The mixed-field reaction indicates a warm autoantibody, and PEG is
known to cause false-positive reactions with autoantibodies.
D. The discrepancy is due to a prozone phenomenon from excess
antibody, which is more common in gel than tube methods.
Correct Answer: B - Gel columns can produce false-negative
results for Kidd antibodies due to their low avidity and dosage
effect, whereas PEG tube testing enhances IgG detection.
RATIONALE
Kidd antibodies exhibit dosage and low avidity, often evading
detection in gel systems, while PEG tube testing increases sensitivity
for IgG. Mixed-field reactions can occur with weak antibodies or
recent transfusion. Warm autoantibodies typically produce
panreactivity, not mixed-field, and prozone is rare in gel.
Question 2
In a massive transfusion protocol (MTP), which of the following ratios of
plasma to red blood cells to platelets is most strongly supported by current
evidence for improving hemostasis in trauma patients?
A. 1:1:1
Page 2
, B. 1:2:1
C. 1:3:1
D. 1:1:2
Correct Answer: A - 1:1:1
RATIONALE
The PROPPR trial demonstrated that a 1:1:1 ratio of
plasma:platelets:RBCs reduces death from exsanguination and
achieves earlier hemostasis compared to 1:1:2. Current AABB and
ATLS guidelines endorse balanced resuscitation with 1:1:1 until
laboratory-guided therapy is available.
Question 3
Which of the following molecular testing methodologies is most appropriate
for resolving a serologic ABO discrepancy in a recently transfused patient with
a history of hematopoietic stem cell transplant?
A. PCR-SSP for ABO alleles
B. Short tandem repeat (STR) analysis
C. Next-generation sequencing (NGS) of the ABO gene
D. Chromosome microarray
Correct Answer: B - Short tandem repeat (STR) analysis
RATIONALE
STR analysis can differentiate donor and recipient DNA, identifying
chimerism after HSCT, which explains mixed-field agglutination and
ABO discrepancies. PCR-SSP and NGS cannot distinguish donor vs
recipient origin; microarray detects copy number changes, not
chimerism.
Page 3
, Question 4
A patient on extracorporeal membrane oxygenation (ECMO) develops
heparin-induced thrombocytopenia (HIT) with a 4T score of 7. Which
anticoagulation strategy is most appropriate for continued ECMO support?
A. Switch to low-molecular-weight heparin
B. Continue unfractionated heparin with close monitoring
C. Argatroban infusion with dose titration to aPTT 1.5-3.0 times baseline
D. Bivalirudin infusion with dose titration to aPTT 1.5-2.5 times baseline
Correct Answer: D - Bivalirudin infusion with dose titration to
aPTT 1.5-2.5 times baseline
RATIONALE
Bivalirudin is preferred for HIT patients on ECMO due to its short
half-life, lack of renal dependence, and predictable pharmacokinetics.
Argatroban is hepatically cleared and may be used but is not first-line
for ECMO. LMWH and UFH are contraindicated in HIT.
Question 5
Which of the following best describes the mechanism by which pathogen
reduction technology (PRT) with amotosalen and UVA light inactivates
pathogens in platelet concentrates?
A. Generation of reactive oxygen species that damage nucleic acids
B. Intercalation into nucleic acids and cross-linking upon UVA
illumination
C. Alkylation of viral proteins preventing receptor binding
D. Photodynamic inactivation of lipid membranes
Correct Answer: B - Intercalation into nucleic acids and
cross-linking upon UVA illumination
Page 4
A patient with a historical anti-Jk^a and a current antibody screen that is
negative by gel but positive by polyethylene glycol (PEG) tube method
demonstrates a mixed-field reaction in the antihuman globulin phase. Which of
the following best explains this discrepancy?
A. Kidd antibodies are classically complement-binding and may be
undetectable by gel due to complement interference, while PEG enhances
IgM detection.
B. Gel columns can produce false-negative results for Kidd antibodies
due to their low avidity and dosage effect, whereas PEG tube testing
enhances IgG detection.
C. The mixed-field reaction indicates a warm autoantibody, and PEG is
known to cause false-positive reactions with autoantibodies.
D. The discrepancy is due to a prozone phenomenon from excess
antibody, which is more common in gel than tube methods.
Correct Answer: B - Gel columns can produce false-negative
results for Kidd antibodies due to their low avidity and dosage
effect, whereas PEG tube testing enhances IgG detection.
RATIONALE
Kidd antibodies exhibit dosage and low avidity, often evading
detection in gel systems, while PEG tube testing increases sensitivity
for IgG. Mixed-field reactions can occur with weak antibodies or
recent transfusion. Warm autoantibodies typically produce
panreactivity, not mixed-field, and prozone is rare in gel.
Question 2
In a massive transfusion protocol (MTP), which of the following ratios of
plasma to red blood cells to platelets is most strongly supported by current
evidence for improving hemostasis in trauma patients?
A. 1:1:1
Page 2
, B. 1:2:1
C. 1:3:1
D. 1:1:2
Correct Answer: A - 1:1:1
RATIONALE
The PROPPR trial demonstrated that a 1:1:1 ratio of
plasma:platelets:RBCs reduces death from exsanguination and
achieves earlier hemostasis compared to 1:1:2. Current AABB and
ATLS guidelines endorse balanced resuscitation with 1:1:1 until
laboratory-guided therapy is available.
Question 3
Which of the following molecular testing methodologies is most appropriate
for resolving a serologic ABO discrepancy in a recently transfused patient with
a history of hematopoietic stem cell transplant?
A. PCR-SSP for ABO alleles
B. Short tandem repeat (STR) analysis
C. Next-generation sequencing (NGS) of the ABO gene
D. Chromosome microarray
Correct Answer: B - Short tandem repeat (STR) analysis
RATIONALE
STR analysis can differentiate donor and recipient DNA, identifying
chimerism after HSCT, which explains mixed-field agglutination and
ABO discrepancies. PCR-SSP and NGS cannot distinguish donor vs
recipient origin; microarray detects copy number changes, not
chimerism.
Page 3
, Question 4
A patient on extracorporeal membrane oxygenation (ECMO) develops
heparin-induced thrombocytopenia (HIT) with a 4T score of 7. Which
anticoagulation strategy is most appropriate for continued ECMO support?
A. Switch to low-molecular-weight heparin
B. Continue unfractionated heparin with close monitoring
C. Argatroban infusion with dose titration to aPTT 1.5-3.0 times baseline
D. Bivalirudin infusion with dose titration to aPTT 1.5-2.5 times baseline
Correct Answer: D - Bivalirudin infusion with dose titration to
aPTT 1.5-2.5 times baseline
RATIONALE
Bivalirudin is preferred for HIT patients on ECMO due to its short
half-life, lack of renal dependence, and predictable pharmacokinetics.
Argatroban is hepatically cleared and may be used but is not first-line
for ECMO. LMWH and UFH are contraindicated in HIT.
Question 5
Which of the following best describes the mechanism by which pathogen
reduction technology (PRT) with amotosalen and UVA light inactivates
pathogens in platelet concentrates?
A. Generation of reactive oxygen species that damage nucleic acids
B. Intercalation into nucleic acids and cross-linking upon UVA
illumination
C. Alkylation of viral proteins preventing receptor binding
D. Photodynamic inactivation of lipid membranes
Correct Answer: B - Intercalation into nucleic acids and
cross-linking upon UVA illumination
Page 4
