CHT/CHS CERTIFICATION-SEROLOGY EXAM-COMPLETE
QUESTIONS AND ANSWERS PLUS DETAILED RATIONALES |
NEWEST STUDYGUIDE | DOWNLOAD INSTANT PDF 2027-2028
1. Which immunoglobulin class is the primary mediator of the primary immune response
and exists typically as a pentameric structure in human serum?
A. IgA
B. IgG
C. IgM
D. IgE
Answer: C
IgM is the first immunoglobulin produced during a primary immune response and circulates
as a pentamer linked by a J chain, providing high avidity for antigen binding.
2. A technologist performs a routine ABO forward typing and observes 4+ agglutination
with Anti-A and 0 reaction with Anti-B. Reverse typing shows 0 reaction with A1 cells and
4+ reaction with B cells. What is the patient's ABO blood group?
A. Group A
B. Group B
C. Group AB
D. Group O
Answer: A
The presence of A antigen on red cells (forward typing) and anti-B antibody in serum (reverse
typing) definitively identifies the individual as Group A.
3. In complement-dependent cytotoxicity (CDC) testing for HLA typing, what role does the
addition of rabbit serum play?
A. Inhibits non-specific antibody binding
B. Serves as a source of exogenous complement
C. Neutralizes anti-HLA antibodies
D. Solubilizes cell membrane proteins
Answer: B
Rabbit complement is added to CDC crossmatching assays because it effectively triggers cell
lysis when anti-HLA antibodies bind to target donor lymphocytes.
,4. What is the primary cause of a false-positive result in a direct antiglobulin test (DAT)?
A. Under-centrifugation of the sample tube
B. Over-centrifugation causing cell packing mistaken for agglutination
C. Failure to wash red blood cells prior to adding antihuman globulin
D. Heat inactivation of complement components
Answer: B
Over-centrifugation forces red blood cells into a tight button that may fail to resuspend
smoothly, leading the technologist to interpret packed cells as true immunological
agglutination.
5. During a serological routine test, a patient sample demonstrates anti-Rh (D) reactivity.
Which of the following immunoglobulins is capable of crossing the placenta to cause
hemolytic disease of the fetus and newborn (HDFN)?
A. IgA
B. IgE
C. IgG
D. IgM
Answer: C
IgG is the only immunoglobulin class actively transported across the human placenta due to
its interaction with neonatal Fc receptors (FcRn).
6. Which HLA locus encodes Class II major histocompatibility antigens?
A. HLA-A
B. HLA-B
C. HLA-C
D. HLA-DR
Answer: D
HLA-DR, along with HLA-DQ and HLA-DP, represents Class II MHC loci responsible for
presenting extracellular antigens to CD4+ T-helper cells.
7. In an enzyme-linked immunosorbent assay (ELISA), what is the function of the substrate
solution?
A. To bind directly to the target capture antibody
B. To react with the enzyme label to produce a measurable signal
C. To block unreacted binding sites on the solid phase matrix
D. To denature contaminating proteins prior to detection
,Answer: B
The substrate reacts with the conjugated enzyme (such as horseradish peroxidase or alkaline
phosphatase) to generate a colorimetric, fluorescent, or chemiluminescent signal proportional
to analyte concentration.
8. Which prozone effect phenomenon occurs in serological agglutination testing?
A. Prozone occurs due to antigen excess, resulting in false negatives.
B. Prozone occurs due to antibody excess, resulting in false negatives.
C. Prozone occurs when complement fails to fix to IgM antibodies.
D. Prozone occurs when ionic strength prevents red cell lattice formation.
Answer: B
Prozone effect refers to antibody excess where monovalent binding prevents cross-linking and
lattice formation, yielding a false-negative agglutination result.
9. What temperature is required for the optimal reactivity of most cold-reacting
autoantibodies (e.g., anti-I)?
A. 37°C
B. 30°C
C. 22°C
D. 4°C
Answer: D
Cold-reacting antibodies demonstrate peak thermal reactivity at 4°C and typically lose
agglutinating activity as temperatures approach 37°C.
10. A serum sample evaluated for HLA antibody screening displays strong reactivity with
all panel cells, including the self-control. What is the most likely cause?
A. Specific HLA Class I alloantibody
B. Presence of an autoantibody or non-HLA artifact
C. High-titer HLA Class II donor antibody
D. Complete absence of complement proteins
Answer: B
Reactivity with all panel cells combined with a positive self-control strongly indicates an
autoantibody or non-specific serological artifact rather than a true alloantibody.
11. Which preservation anticoagulant solution allows red blood cells to be stored for up to
35 days at 1°C to 6°C?
, A. ACD (Acid Citrate Dextrose)
B. CPD (Citrate Phosphate Dextrose)
C. CPDA-1 (Citrate Phosphate Dextrose Adenine)
D. Heparin
Answer: C
CPDA-1 provides adenine to maintain ATP synthesis within red cells, extending blood unit
shelf-life to 35 days compared to 21 days for CPD.
12. In flow cytometric crossmatching (FCXM), what does a high median fluorescence
intensity (MFI) shift on T cells indicate?
A. Presence of anti-HLA Class II donor-specific antibodies
B. Presence of anti-HLA Class I donor-specific antibodies
C. Non-specific binding of secondary fluorescent dyes to B cells
D. Absence of cytotoxic complement proteins in donor serum
Answer: B
T lymphocytes express Class I HLA antigens predominantly; therefore, a positive T-cell flow
crossmatch specifically signifies anti-HLA Class I donor-specific antibodies.
13. Which of the following reagents is used to neutralize anti-P1 antibody interference
during red cell antibody identification?
A. Dithiothreitol (DTT)
B. Hydatid cyst fluid
C. Ficin enzyme
D. Polyethylene glycol (PEG)
Answer: B
P1 substance isolated from soluble sources like hydatid cyst fluid or pigeon egg whites
specifically neutralizes anti-P1 antibodies in patient serum.
14. What is the standard concentration of red cell suspensions used in tube-based blood
bank serology testing?
A. 0.5% to 1%
B. 2% to 5%
C. 8% to 10%
D. 12% to 15%
Answer: B
QUESTIONS AND ANSWERS PLUS DETAILED RATIONALES |
NEWEST STUDYGUIDE | DOWNLOAD INSTANT PDF 2027-2028
1. Which immunoglobulin class is the primary mediator of the primary immune response
and exists typically as a pentameric structure in human serum?
A. IgA
B. IgG
C. IgM
D. IgE
Answer: C
IgM is the first immunoglobulin produced during a primary immune response and circulates
as a pentamer linked by a J chain, providing high avidity for antigen binding.
2. A technologist performs a routine ABO forward typing and observes 4+ agglutination
with Anti-A and 0 reaction with Anti-B. Reverse typing shows 0 reaction with A1 cells and
4+ reaction with B cells. What is the patient's ABO blood group?
A. Group A
B. Group B
C. Group AB
D. Group O
Answer: A
The presence of A antigen on red cells (forward typing) and anti-B antibody in serum (reverse
typing) definitively identifies the individual as Group A.
3. In complement-dependent cytotoxicity (CDC) testing for HLA typing, what role does the
addition of rabbit serum play?
A. Inhibits non-specific antibody binding
B. Serves as a source of exogenous complement
C. Neutralizes anti-HLA antibodies
D. Solubilizes cell membrane proteins
Answer: B
Rabbit complement is added to CDC crossmatching assays because it effectively triggers cell
lysis when anti-HLA antibodies bind to target donor lymphocytes.
,4. What is the primary cause of a false-positive result in a direct antiglobulin test (DAT)?
A. Under-centrifugation of the sample tube
B. Over-centrifugation causing cell packing mistaken for agglutination
C. Failure to wash red blood cells prior to adding antihuman globulin
D. Heat inactivation of complement components
Answer: B
Over-centrifugation forces red blood cells into a tight button that may fail to resuspend
smoothly, leading the technologist to interpret packed cells as true immunological
agglutination.
5. During a serological routine test, a patient sample demonstrates anti-Rh (D) reactivity.
Which of the following immunoglobulins is capable of crossing the placenta to cause
hemolytic disease of the fetus and newborn (HDFN)?
A. IgA
B. IgE
C. IgG
D. IgM
Answer: C
IgG is the only immunoglobulin class actively transported across the human placenta due to
its interaction with neonatal Fc receptors (FcRn).
6. Which HLA locus encodes Class II major histocompatibility antigens?
A. HLA-A
B. HLA-B
C. HLA-C
D. HLA-DR
Answer: D
HLA-DR, along with HLA-DQ and HLA-DP, represents Class II MHC loci responsible for
presenting extracellular antigens to CD4+ T-helper cells.
7. In an enzyme-linked immunosorbent assay (ELISA), what is the function of the substrate
solution?
A. To bind directly to the target capture antibody
B. To react with the enzyme label to produce a measurable signal
C. To block unreacted binding sites on the solid phase matrix
D. To denature contaminating proteins prior to detection
,Answer: B
The substrate reacts with the conjugated enzyme (such as horseradish peroxidase or alkaline
phosphatase) to generate a colorimetric, fluorescent, or chemiluminescent signal proportional
to analyte concentration.
8. Which prozone effect phenomenon occurs in serological agglutination testing?
A. Prozone occurs due to antigen excess, resulting in false negatives.
B. Prozone occurs due to antibody excess, resulting in false negatives.
C. Prozone occurs when complement fails to fix to IgM antibodies.
D. Prozone occurs when ionic strength prevents red cell lattice formation.
Answer: B
Prozone effect refers to antibody excess where monovalent binding prevents cross-linking and
lattice formation, yielding a false-negative agglutination result.
9. What temperature is required for the optimal reactivity of most cold-reacting
autoantibodies (e.g., anti-I)?
A. 37°C
B. 30°C
C. 22°C
D. 4°C
Answer: D
Cold-reacting antibodies demonstrate peak thermal reactivity at 4°C and typically lose
agglutinating activity as temperatures approach 37°C.
10. A serum sample evaluated for HLA antibody screening displays strong reactivity with
all panel cells, including the self-control. What is the most likely cause?
A. Specific HLA Class I alloantibody
B. Presence of an autoantibody or non-HLA artifact
C. High-titer HLA Class II donor antibody
D. Complete absence of complement proteins
Answer: B
Reactivity with all panel cells combined with a positive self-control strongly indicates an
autoantibody or non-specific serological artifact rather than a true alloantibody.
11. Which preservation anticoagulant solution allows red blood cells to be stored for up to
35 days at 1°C to 6°C?
, A. ACD (Acid Citrate Dextrose)
B. CPD (Citrate Phosphate Dextrose)
C. CPDA-1 (Citrate Phosphate Dextrose Adenine)
D. Heparin
Answer: C
CPDA-1 provides adenine to maintain ATP synthesis within red cells, extending blood unit
shelf-life to 35 days compared to 21 days for CPD.
12. In flow cytometric crossmatching (FCXM), what does a high median fluorescence
intensity (MFI) shift on T cells indicate?
A. Presence of anti-HLA Class II donor-specific antibodies
B. Presence of anti-HLA Class I donor-specific antibodies
C. Non-specific binding of secondary fluorescent dyes to B cells
D. Absence of cytotoxic complement proteins in donor serum
Answer: B
T lymphocytes express Class I HLA antigens predominantly; therefore, a positive T-cell flow
crossmatch specifically signifies anti-HLA Class I donor-specific antibodies.
13. Which of the following reagents is used to neutralize anti-P1 antibody interference
during red cell antibody identification?
A. Dithiothreitol (DTT)
B. Hydatid cyst fluid
C. Ficin enzyme
D. Polyethylene glycol (PEG)
Answer: B
P1 substance isolated from soluble sources like hydatid cyst fluid or pigeon egg whites
specifically neutralizes anti-P1 antibodies in patient serum.
14. What is the standard concentration of red cell suspensions used in tube-based blood
bank serology testing?
A. 0.5% to 1%
B. 2% to 5%
C. 8% to 10%
D. 12% to 15%
Answer: B
