3.3 Flashcards
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
B. Detected 1-3 weeks after appearance of the primary chancre
What substance is detected by the rapid plasma reagin (RPR) and Venereal Disease Research Laboratory (VDRL) tests for syphilis?
A. Cardiolipin
B. Anticardiolipin antibody
C. Anti-T. pallidum antibody
D. Treponema pallidum
B. Anticardiolipin antibody
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
C. Cardiolipin
Which of the following is the most sensitive test to detect congenital syphilis?
A. VDRL
B. RPR
C. Microhemagglutinin test for T. pallidum (MHA-TP)
D. Polymerase chain reaction (PCR)
D. Polymerase chain reaction (PCR)
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
B. Fluorescent T. pallidum antibody absorption test (FTA-ABS)
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
D. Treponema pallidum particle agglutination (TP-PA) test
Which test is most likely to be positive in the tertiary stage of syphilis?
A. FTA-ABS
B. RPR
C. VDRL
D. Reagin screen test (RST)
A. FTA-ABS
What is the most likely interpretation of the following syphilis serological results?
RPR: reactive; VDRL: reactive; MHA-TP: nonreactive
A. Neurosyphilis
B. Secondary syphilis
C. Syphilis that has been successfully treated
D. Biological false positive
D. Biological false positive
Which specimen is the sample of choice to evaluate latent or tertiary syphilis?
A. Serum sample
B. Chancre fluid
C. CSF
D. Joint fluid
C. CSF
Interpret the following quantitative RPR test
results.
RPR titer: weakly reactive 1:8; reactive 1:8-1:64
A. Excess antibody, prozone effect
B. Excess antigen, postzone effect
C. Equivalence of antigen and antibody
D. Impossible to interpret; testing error
A. Excess antibody, prozone effect
Tests to identify infection with HIV fall into which three general classification types of tests?
A. Tissue culture, antigen, and antibody tests
B. Tests for antigens, antibodies, and nucleic acid
C. DNA probe, DNA amplification, and Western
blot tests
D. ELISA, Western blot, and Southern blot tests
B. Tests for antigens, antibodies, and nucleic acid
Which tests are considered screening tests for HIV?
A. ELISA, 4th generation, and rapid antibody tests
B. Immunofluorescence, Western blot, radioimmuno-precipitation assay
C. Culture, antigen capture assay, DNA amplification
D. Reverse transcriptase and messenger RNA (mRNA) assay
A. ELISA, 4th generation, and rapid antibody tests
Which tests are considered confirmatory tests for HIV?
A. ELISA and rapid antibody tests
B. Western blot test, HIC-1,2 differentiation assays, and polymerase chain reaction
C. Culture, antigen capture assay, polymerase chain reaction
D. Reverse transcriptase and mRNA assay
B. Western blot test, HIC-1,2 differentiation assays, and polymerase chain reaction
Which is most likely a positive Western blot result for infection with HIV?
A. Band at p24
B. Band at gp60
C. Bands at p24 and p31
D. Bands at p24 and gp120
D. Bands at p24 and gp120
A woman who has had five pregnancies subsequently tests positive for HIV by Western blot. What is the most likely reason for this result?
A. Possible cross-reaction with herpes or EBV antibodies
B. Interference from medication
C. Cross-reaction with HLA antigens in the antigen preparation
D. Possible technical error
C. Cross-reaction with HLA antigens in the antigen preparation
Interpret the following results for HIV infection.
ELISA: positive; repeat ELISA: negative; Western blot:
no bands
A. Positive for HIV
B. Negative for HIV
C. Indeterminate
D. Further testing needed
B. Negative for HIV
Interpret the following results for HIV infection.
HIV 1,2 ELISA: positive; HIV-1 Western blot: indeterminate; HIV-1 p24 antigen: negative
A. Positive for antibodies to human immunodeficiency virus, HIV-1
B. Positive for antibodies to human immunodeficiency virus, HIV-2
C. Cross reaction; biological false-positive result
D. Additional testing required
D. Additional testing required
What is the most likely explanation when antibody tests for HIV are negative but a polymerase chain reaction test performed 1 week later is positive?
A. Probably not HIV infection
B. Patient is in the “window phase” before antibody production
C. Tests were performed incorrectly
D. Clinical signs may be misinterpreted
B. Patient is in the “window phase” before antibody production
What criteria constitute the classification system for HIV infection?
A. CD4-positive T-cell count and clinical symptoms
B. Clinical symptoms, condition, duration, and number of positive bands on Western blot
C. Presence or absence of lymphadenopathy
D. Positive bands on Western blot and CD8-positive T-cell count
A. CD4-positive T-cell count and clinical symptoms
What is the main difficulty associated with the development of an HIV vaccine?
A. The virus has been difficult to culture; antigen extraction and concentration are extremely laborious
B. Human trials cannot be performed
C. Different strains of the virus are genetically diverse
D. Anti-idiotype antibodies cannot be developed
C. Different strains of the virus are genetically diverse
Which CD4:CD8 ratio is most likely in a patient with acquired immunodeficiency syndrome (AIDS)?
A. 2:1
B. 3:1
C. 2:3
D. 1:2
D. 1:2
What is the advantage of 4th-generation rapid HIV tests over earlier rapid HIV tests?
A. They use recombinant antigens
B. They detect multiple strains of HIV
C. They detect p24 antigen
D. They are quantitative
C. They detect p24 antigen
Which method is used to test for HIV infection in infants who are born to HIV-positive mothers?
A. ELISA
B. Western blot test
C. Polymerase chain reaction
D. Viral culture
C. Polymerase chain reaction
What is the most likely cause when a Western blot or ELISA is positive for all controls and samples?
A. Improper pipetting
B. Improper washing
C. Improper addition of sample
D. Improper reading
B. Improper washing