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Medical Laboratory Science Review Harr. -
3.3 Immunology and Serology: Infectious
Disease Questions and Answers
1. Which serum antibody response usually characterizes the
primary (early) stage of syphilis?
A. Antibodies against syphilis are undetectable
B. Detected 1-3 weeks after appearance of the primary chancre
C. Detected in 50% of cases before the primary chancre disappears
D. Detected within 2 weeks after infection Ans: B. Detected 1-3
weeks after appearance of the primary chancre
During the primary stage of syphilis, about 90% of patients
develop antibodies between 1 and 3 weeks after the appearance of
the primary chancre.
2. What substance is detected by the rapid plasma reagin (RPR)
and Venereal Disease Research Laboratory (VDRL) tests for
syphilis?
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A. Cardiolipin
B. Anticardiolipin antibody
C. Anti-T. pallidum antibody
D. Treponema pallidum Ans: B. Anticardiolipin antibody
B Reagin is the name for a nontreponemal antibody that appears in
the serum of syphilis-infected persons and is detected by the RPR
and VDRL assays. Reagin reacts with cardiolipin, a lipid-rich
extract of beef heart and other animal tissues.
3. What type of antigen is used in the RPR card test?
A. Live treponemal organisms
B. Killed suspension of treponemal organisms
C. Cardiolipin
D. Tanned sheep cells Ans: C. Cardiolipin
Cardiolipin is extracted from animal tissues, such as beef hearts,
and attached to carbon particles. In the presence of reagin, the
particles will agglutinate.
4. Which of the following is the most sensitive test to detect
congenital syphilis?
A. VDRL
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B. RPR
C. Microhemagglutinin test for T. pallidum (MHA-TP)
D. Polymerase chain reaction (PCR) Ans: D. Polymerase chain
reaction (PCR)
The PCR will amplify a very small amount of DNA from T.
pallidum and allow for detection of the organism in the infant.
Antibody tests such as VDRL and RPR may detect maternal
antibody only, not indicating if the infant has been infected.
5. A biological false-positive reaction is least likely with which test
for syphilis?
A. VDRL
B. Fluorescent T. pallidum antibody absorption test (FTA-ABS)
C. RPR
D. All are equally likely to detect a false-positive result Ans: B.
Fluorescent T. pallidum antibody absorption test (FTA-ABS)
The FTA-ABS test is more specific for T. pallidum than
nontreponemal tests such as the VDRL and RPR and would be least
likely to detect a biological false-positive result. The FTA-ABS test
uses heat-inactivated serum that has been absorbed with the Reiter
strain of T. pallidum to remove nonspecific antibodies.
Nontreponemal tests have a biological false-positive rate of 1%-
10%, depending upon the patient population tested. False-positive
findings are caused commonly by infectious mononucleosis (IM),
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SLE, viral hepatitis, and human immunodeficiency virus (HIV)
infection.
6. A 12-year old girl has symptoms of fatigue and a localized
lymphadenopathy. Laboratory tests reveal a peripheral blood
lymphocytosis, a positive RPR, and a positive spot test for IM.
What test should be performed next?
A. HIV test by ELISA
B. VDRL
C. Epstein-Barr virus (EBV) specific antigen test
D. Treponema pallidum particle agglutination (TP-PA) test Ans: D.
Treponema pallidum particle agglutination (TP-PA) test
The patient's symptoms are nonspecific and could be attributed to
many potential causes. However, the patient's age, lymphocytosis,
and serological results point to infectious mononucleosis (IM). The
rapid spot test for antibodies seen in IM is highly specific. The
EBV-specific antigen test is more sensitive but is unnecessary when
the spot test is positive. HIV infection is uncommon at this age
and is often associated with generalized lymphadenopathy and a
normal or reduced total lymphocyte count. IM antibodies are
commonly implicated as a cause of biological false-positive
nontreponemal tests for syphilis. Therefore, a treponemal test for
syphilis should be performed to document this phenomenon in
this case
7. Which test is most likely to be positive in the tertiary stage of
syphilis?
© 2025 All rights reserved
Medical Laboratory Science Review Harr. -
3.3 Immunology and Serology: Infectious
Disease Questions and Answers
1. Which serum antibody response usually characterizes the
primary (early) stage of syphilis?
A. Antibodies against syphilis are undetectable
B. Detected 1-3 weeks after appearance of the primary chancre
C. Detected in 50% of cases before the primary chancre disappears
D. Detected within 2 weeks after infection Ans: B. Detected 1-3
weeks after appearance of the primary chancre
During the primary stage of syphilis, about 90% of patients
develop antibodies between 1 and 3 weeks after the appearance of
the primary chancre.
2. What substance is detected by the rapid plasma reagin (RPR)
and Venereal Disease Research Laboratory (VDRL) tests for
syphilis?
© 2025 All rights reserved
, 2 | Page
A. Cardiolipin
B. Anticardiolipin antibody
C. Anti-T. pallidum antibody
D. Treponema pallidum Ans: B. Anticardiolipin antibody
B Reagin is the name for a nontreponemal antibody that appears in
the serum of syphilis-infected persons and is detected by the RPR
and VDRL assays. Reagin reacts with cardiolipin, a lipid-rich
extract of beef heart and other animal tissues.
3. What type of antigen is used in the RPR card test?
A. Live treponemal organisms
B. Killed suspension of treponemal organisms
C. Cardiolipin
D. Tanned sheep cells Ans: C. Cardiolipin
Cardiolipin is extracted from animal tissues, such as beef hearts,
and attached to carbon particles. In the presence of reagin, the
particles will agglutinate.
4. Which of the following is the most sensitive test to detect
congenital syphilis?
A. VDRL
© 2025 All rights reserved
, 3 | Page
B. RPR
C. Microhemagglutinin test for T. pallidum (MHA-TP)
D. Polymerase chain reaction (PCR) Ans: D. Polymerase chain
reaction (PCR)
The PCR will amplify a very small amount of DNA from T.
pallidum and allow for detection of the organism in the infant.
Antibody tests such as VDRL and RPR may detect maternal
antibody only, not indicating if the infant has been infected.
5. A biological false-positive reaction is least likely with which test
for syphilis?
A. VDRL
B. Fluorescent T. pallidum antibody absorption test (FTA-ABS)
C. RPR
D. All are equally likely to detect a false-positive result Ans: B.
Fluorescent T. pallidum antibody absorption test (FTA-ABS)
The FTA-ABS test is more specific for T. pallidum than
nontreponemal tests such as the VDRL and RPR and would be least
likely to detect a biological false-positive result. The FTA-ABS test
uses heat-inactivated serum that has been absorbed with the Reiter
strain of T. pallidum to remove nonspecific antibodies.
Nontreponemal tests have a biological false-positive rate of 1%-
10%, depending upon the patient population tested. False-positive
findings are caused commonly by infectious mononucleosis (IM),
© 2025 All rights reserved
, 4 | Page
SLE, viral hepatitis, and human immunodeficiency virus (HIV)
infection.
6. A 12-year old girl has symptoms of fatigue and a localized
lymphadenopathy. Laboratory tests reveal a peripheral blood
lymphocytosis, a positive RPR, and a positive spot test for IM.
What test should be performed next?
A. HIV test by ELISA
B. VDRL
C. Epstein-Barr virus (EBV) specific antigen test
D. Treponema pallidum particle agglutination (TP-PA) test Ans: D.
Treponema pallidum particle agglutination (TP-PA) test
The patient's symptoms are nonspecific and could be attributed to
many potential causes. However, the patient's age, lymphocytosis,
and serological results point to infectious mononucleosis (IM). The
rapid spot test for antibodies seen in IM is highly specific. The
EBV-specific antigen test is more sensitive but is unnecessary when
the spot test is positive. HIV infection is uncommon at this age
and is often associated with generalized lymphadenopathy and a
normal or reduced total lymphocyte count. IM antibodies are
commonly implicated as a cause of biological false-positive
nontreponemal tests for syphilis. Therefore, a treponemal test for
syphilis should be performed to document this phenomenon in
this case
7. Which test is most likely to be positive in the tertiary stage of
syphilis?
© 2025 All rights reserved
