SBB (SPECIALIST IN BLOOD BANKING) ASCP
Actual PRACTICE TEST – Comprehensive
Review & Verified Guide
SECTION 1: Advanced Immunohematology & Antibody Identification
(Questions 1-25)
Q1: A 62-year-old male with myelodysplastic syndrome requires transfusion. His
antibody screen is positive. Panel results show:
● 2+ reactions at IS and AHG phases with all panel cells
● Negative autocontrol
● DTT-treated panel: reactions become negative
Patient phenotype: Jk(a-b-)
● What is the MOST likely antibody specificity and the appropriate next step for
providing compatible blood?
A) Anti-P1; crossmatch Jk(a-) units
B) HTLA antibody; perform adsorption studies with Jk(a-) RBCs
C) Anti-I; use pre-warmed technique for crossmatch
D) Antibody to a high-frequency antigen; request rare donor search
Correct Answer: B
COMPLETE SOLUTION:
, ● SBB Competency: Identification of High-Titer Low-Avidity (HTLA) antibodies and
resolution strategy.
● Decision Pathway:
○ Panreactivity at AHG phase suggests antibody to high-frequency antigen
or HTLA.
○ Negative autocontrol rules out autoantibody.
○ Key Clue: Reactions ablated by DTT treatment is characteristic of
antibodies to the Knops/McCoy blood group systems (anti-Kn^a, -McC^a,
-Sl^a, -Yk^a), which are classic HTLA antibodies.
○ The Jk(a-b-) phenotype is a known association with reduced expression of
complement receptor 1 (CR1), which carries Knops antigens, but it's not
the direct cause of the antibody.
○ Appropriate SBB Action: Perform an alloadsorption with phenotypically
similar (Jk(a-)) RBCs to remove the HTLA antibody and check for
underlying clinically significant antibodies. Then crossmatch with
adsorbed serum.
● Evidence/Standard: AABB Technical Manual, 20th Ed., Chapter 19: "Antibodies of
Undetermined Specificity" details HTLA characteristics and resolution.
● Distractor Analysis:
○ A: Incorrect. Anti-P1 is typically a cold-reactive IgM antibody, not
panreactive at AHG, and not DTT-sensitive.
○ C: Incorrect. Anti-I is a cold autoantibody; autocontrol would typically be
positive, and it is not DTT-sensitive.
○ D: Incorrect. While the antibody is to a high-frequency antigen, HTLA
antibodies are often not clinically significant. A rare donor search is
premature and unnecessary before adsorption studies to rule out other
antibodies.
● Clinical Implication: Mistaking an HTLA antibody for a clinically significant one
could trigger an unnecessary, costly, and time-consuming rare donor search,
delaying transfusion for a patient who may safely receive antigen-unscreened
blood after appropriate investigation.
Q2: A reference lab receives a sample from a pregnant woman (G3P2) at 28 weeks
gestation. Her antibody screen is positive with anti-D identified. Her titer is 64 by IAGT.
Her history indicates one previous pregnancy with an unaffected child. What is the
MOST appropriate recommendation to the managing obstetrician?
,A) Perform amniocentesis for fetal genotyping and ΔOD450 immediately
B) Schedule weekly middle cerebral artery (MCA) Doppler peak systolic velocity
measurements starting now
C) Repeat the titer in 4 weeks; if it remains stable or rises slowly, continue monitoring
with MCA Dopplers starting at 32 weeks
D) Admit for intrauterine transfusion (IUT) based on the high titer and gestational age
Correct Answer: C
COMPLETE SOLUTION:
● SBB Competency: Management and monitoring of HDFN risk in consultation with
clinical team.
● Decision Pathway:
○ Critical History: Previous unaffected child significantly reduces current risk
despite a titer of 64.
○ AABB/American College of Obstetricians and Gynecologists (ACOG)
Guidelines: For anti-D, a critical titer (threshold for increased monitoring) is
institution-specific but often 16-32. A titer of 64 warrants increased
surveillance.
○ Standard of Care: With a previous unaffected pregnancy, invasive testing
(amniocentesis) is not first-line. Serial MCA Doppler ultrasound is the
non-invasive monitoring method of choice for detecting fetal anemia.
○ Timing: MCA Doppler monitoring typically begins at 24-28 weeks for
high-risk cases, but given the reassuring history, starting at 32 weeks after
confirming titer trend is acceptable and evidence-based.
● Evidence/Standard: AABB Technical Manual, Chapter 26; ACOG Practice Bulletin
No. 192 (2018) on Management of Alloimmunization.
● Distractor Analysis:
○ A: Incorrect. Amniocentesis carries a risk of miscarriage/fetal loss and is
not indicated as a first step, especially with a previous unaffected child. It
is reserved for cases where MCA Dopplers are elevated or inconclusive.
, ○ B: Incorrect. Weekly MCA starting immediately at 28 weeks is overly
aggressive given the patient's history. The titer should be repeated to
establish a trend.
○ D: Incorrect. IUT is a high-risk procedure reserved for fetuses with
documented severe anemia (by MCA Doppler or cordocentesis), not based
on maternal titer alone.
● Clinical Implication: Providing incorrect, overly aggressive recommendations can
subject the mother and fetus to unnecessary invasive procedures with inherent
risks. The SBB role is to provide precise, evidence-based consultative guidance.
Q3: A 34-year-old female with warm autoimmune hemolytic anemia (WAIHA) requires
transfusion. Her records indicate previous anti-c and anti-E. Current workup shows:
● Positive DAT: 3+ with anti-IgG, negative with anti-C3d
● Autocontrol: 3+ at AHG
● All panel cells positive at AHG (including autologous cells)
No discrete specificity identified in panel
● What is the MOST appropriate strategy to provide compatible blood?
A) Perform a cold autoadsorption to remove the autoantibody
B) Perform multiple warm autoadsorptions and phenotype the adsorbed serum for
underlying alloantibodies
C) Crossmatch random units and select the least incompatible units
D) Request rare c- and E-negative blood from the frozen inventory
Correct Answer: B
COMPLETE SOLUTION:
● SBB Competency: Complex resolution of autoantibodies with a history of
clinically significant alloantibodies.
● Decision Pathway:
Actual PRACTICE TEST – Comprehensive
Review & Verified Guide
SECTION 1: Advanced Immunohematology & Antibody Identification
(Questions 1-25)
Q1: A 62-year-old male with myelodysplastic syndrome requires transfusion. His
antibody screen is positive. Panel results show:
● 2+ reactions at IS and AHG phases with all panel cells
● Negative autocontrol
● DTT-treated panel: reactions become negative
Patient phenotype: Jk(a-b-)
● What is the MOST likely antibody specificity and the appropriate next step for
providing compatible blood?
A) Anti-P1; crossmatch Jk(a-) units
B) HTLA antibody; perform adsorption studies with Jk(a-) RBCs
C) Anti-I; use pre-warmed technique for crossmatch
D) Antibody to a high-frequency antigen; request rare donor search
Correct Answer: B
COMPLETE SOLUTION:
, ● SBB Competency: Identification of High-Titer Low-Avidity (HTLA) antibodies and
resolution strategy.
● Decision Pathway:
○ Panreactivity at AHG phase suggests antibody to high-frequency antigen
or HTLA.
○ Negative autocontrol rules out autoantibody.
○ Key Clue: Reactions ablated by DTT treatment is characteristic of
antibodies to the Knops/McCoy blood group systems (anti-Kn^a, -McC^a,
-Sl^a, -Yk^a), which are classic HTLA antibodies.
○ The Jk(a-b-) phenotype is a known association with reduced expression of
complement receptor 1 (CR1), which carries Knops antigens, but it's not
the direct cause of the antibody.
○ Appropriate SBB Action: Perform an alloadsorption with phenotypically
similar (Jk(a-)) RBCs to remove the HTLA antibody and check for
underlying clinically significant antibodies. Then crossmatch with
adsorbed serum.
● Evidence/Standard: AABB Technical Manual, 20th Ed., Chapter 19: "Antibodies of
Undetermined Specificity" details HTLA characteristics and resolution.
● Distractor Analysis:
○ A: Incorrect. Anti-P1 is typically a cold-reactive IgM antibody, not
panreactive at AHG, and not DTT-sensitive.
○ C: Incorrect. Anti-I is a cold autoantibody; autocontrol would typically be
positive, and it is not DTT-sensitive.
○ D: Incorrect. While the antibody is to a high-frequency antigen, HTLA
antibodies are often not clinically significant. A rare donor search is
premature and unnecessary before adsorption studies to rule out other
antibodies.
● Clinical Implication: Mistaking an HTLA antibody for a clinically significant one
could trigger an unnecessary, costly, and time-consuming rare donor search,
delaying transfusion for a patient who may safely receive antigen-unscreened
blood after appropriate investigation.
Q2: A reference lab receives a sample from a pregnant woman (G3P2) at 28 weeks
gestation. Her antibody screen is positive with anti-D identified. Her titer is 64 by IAGT.
Her history indicates one previous pregnancy with an unaffected child. What is the
MOST appropriate recommendation to the managing obstetrician?
,A) Perform amniocentesis for fetal genotyping and ΔOD450 immediately
B) Schedule weekly middle cerebral artery (MCA) Doppler peak systolic velocity
measurements starting now
C) Repeat the titer in 4 weeks; if it remains stable or rises slowly, continue monitoring
with MCA Dopplers starting at 32 weeks
D) Admit for intrauterine transfusion (IUT) based on the high titer and gestational age
Correct Answer: C
COMPLETE SOLUTION:
● SBB Competency: Management and monitoring of HDFN risk in consultation with
clinical team.
● Decision Pathway:
○ Critical History: Previous unaffected child significantly reduces current risk
despite a titer of 64.
○ AABB/American College of Obstetricians and Gynecologists (ACOG)
Guidelines: For anti-D, a critical titer (threshold for increased monitoring) is
institution-specific but often 16-32. A titer of 64 warrants increased
surveillance.
○ Standard of Care: With a previous unaffected pregnancy, invasive testing
(amniocentesis) is not first-line. Serial MCA Doppler ultrasound is the
non-invasive monitoring method of choice for detecting fetal anemia.
○ Timing: MCA Doppler monitoring typically begins at 24-28 weeks for
high-risk cases, but given the reassuring history, starting at 32 weeks after
confirming titer trend is acceptable and evidence-based.
● Evidence/Standard: AABB Technical Manual, Chapter 26; ACOG Practice Bulletin
No. 192 (2018) on Management of Alloimmunization.
● Distractor Analysis:
○ A: Incorrect. Amniocentesis carries a risk of miscarriage/fetal loss and is
not indicated as a first step, especially with a previous unaffected child. It
is reserved for cases where MCA Dopplers are elevated or inconclusive.
, ○ B: Incorrect. Weekly MCA starting immediately at 28 weeks is overly
aggressive given the patient's history. The titer should be repeated to
establish a trend.
○ D: Incorrect. IUT is a high-risk procedure reserved for fetuses with
documented severe anemia (by MCA Doppler or cordocentesis), not based
on maternal titer alone.
● Clinical Implication: Providing incorrect, overly aggressive recommendations can
subject the mother and fetus to unnecessary invasive procedures with inherent
risks. The SBB role is to provide precise, evidence-based consultative guidance.
Q3: A 34-year-old female with warm autoimmune hemolytic anemia (WAIHA) requires
transfusion. Her records indicate previous anti-c and anti-E. Current workup shows:
● Positive DAT: 3+ with anti-IgG, negative with anti-C3d
● Autocontrol: 3+ at AHG
● All panel cells positive at AHG (including autologous cells)
No discrete specificity identified in panel
● What is the MOST appropriate strategy to provide compatible blood?
A) Perform a cold autoadsorption to remove the autoantibody
B) Perform multiple warm autoadsorptions and phenotype the adsorbed serum for
underlying alloantibodies
C) Crossmatch random units and select the least incompatible units
D) Request rare c- and E-negative blood from the frozen inventory
Correct Answer: B
COMPLETE SOLUTION:
● SBB Competency: Complex resolution of autoantibodies with a history of
clinically significant alloantibodies.
● Decision Pathway:
