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
What constitutes a diagnosis of viral hepatitis?
A. Abnormal test results for liver enzymes
B. Clinical signs and symptoms
C. Positive results for hepatitis markers
D. All of these options
D. All of these options
Which of the following statements regarding infection with hepatitis D virus is true?
A. Occurs in patients with HIV infection
B. Does not progress to chronic hepatitis
C. Occurs in patients with hepatitis B
D. Is not spread through blood or sexual contact
C. Occurs in patients with hepatitis B
All of the following hepatitis viruses are spread through blood or blood products except:
A. Hepatitis A
B. Hepatitis B
C. Hepatitis C
D. Hepatitis D
A. Hepatitis A
Which hepatitis B marker is the best indicator of early acute infection?
A. HBsAg
B. HBeAg
C. Anti-HBc
D. Anti-HBs
A. HBsAg
Which is the first antibody detected in serum after infection with hepatitis B virus (HBV)?
A. Anti-HBs
B. Anti-HBc IgM
C. Anti-HBe
D. All are detectable at the same time
B. Anti-HBc IgM
Which antibody persists in low-level carriers of hepatitis B virus?
A. IgM anti-HBc
B. IgG anti-HBc
C. IgM anti-HBe
D. IgG anti-HBs
B. IgG anti-HBc
What is the most likely explanation when a patient has clinical signs of viral hepatitis but tests negative for hepatitis A IgM, hepatitis B surface antigen, and hepatitis C Ab?
A. Tests were performed improperly
B. The patient does not have hepatitis
C. The patient may be in the “core window”
D. Clinical evaluation was performed improperly
C. The patient may be in the “core window”
Which hepatitis B markers should be performed on blood products?
A. HBsAg and anti-HBc
B. Anti-HBs and anti-HBc
C. HBeAg and HBcAg
D. Anti-HBs and HBeAg
A. HBsAg and anti-HBc
Which hepatitis antibody confers immunity against reinfection with hepatitis B virus?
A. Anti-HBc IgM
B. Anti-HBc IgG
C. Anti-HBe
D. Anti-HBs
D. Anti-HBs
Which test, other than serological markers, is most consistently elevated in viral hepatitis?
A. Antinuclear antibodies
B. Alanine aminotransferase (ALT)
C. Absolute lymphocyte count
D. Lactate dehydrogenase
B. Alanine aminotransferase (ALT)
If only anti-HBs is positive, which of the following can be ruled out?
A. Hepatitis B virus vaccination
B. Distant past infection with hepatitis B virus
C. Hepatitis B immune globulin (HBIG) injection
D. Chronic hepatitis B virus infection
D. Chronic hepatitis B virus infection
Interpret the following results for EBV infection:
IgG and IgM antibodies to viral capsid antigen (VCA) are positive.
A. Infection in the past
B. Infection with a mutual enhancer virus such as HIV
C. Current infection
D. Impossible to interpret; need more information
C. Current infection
Which statement concerning non-Forssman heterophile antibody is true?
A. It is not absorbed by guinea pig antigen
B. It is absorbed by guinea pig antigen
C. It does not agglutinate horse RBCs
D. It does not agglutinate sheep RBCs
A. It is not absorbed by guinea pig antigen
Given a heterophile antibody titer of 224, which of the following results indicate IM?
Absorption with Guinea Beef Cells | Absorption with Pig Kidney
A. Two-tube titer reduction | Five-tube titer reduction
B. No titer reduction | No titer reduction
C. Five-tube titer reduction | Five-tube titer reduction
D. Five-tube titer reduction | No titer reduction
A. Two-tube titer reduction | Five-tube titer reduction
Given a heterophile antibody titer of 224, which of the following results indicate serum sickness?
Absorption with Guinea Beef Cells | Absorption with Pig Kidney
A. Two-tube titer reduction | Five-tube titer reduction
B. No titer reduction | No titer reduction
C. Five-tube titer reduction | Five-tube titer reduction
D. Five-tube titer reduction | No titer reduction
C. Five-tube titer reduction | Five-tube titer reduction
Given a heterophile antibody titer of 224, which of the following results indicate an error in testing?
Absorption with Guinea Beef Cells | Absorption with Pig Kidney
A. Two-tube titer reduction | Five-tube titer reduction
B. No titer reduction | No titer reduction
C. Five-tube titer reduction | Five-tube titer reduction
D. Five-tube titer reduction | No titer reduction
B. No titer reduction | No titer reduction
Blood products are tested for which virus before being transfused to newborns?
A. EBV
B. Human T-lymphotropic virus II (HTLV-II)
C. Cytomegalovirus (CMV)
D. Hepatitis D virus
C. Cytomegalovirus (CMV)
What is the endpoint for the antistreptolysin O (ASO) latex agglutination assay?
A. Highest serum dilution that shows no agglutination
B. Highest serum dilution that shows agglutination
C. Lowest serum dilution that shows agglutination
D. Lowest serum dilution that shows no agglutination
B. Highest serum dilution that shows agglutination
Interpret the following ASO results:
Tube Nos. 1-4 (Todd unit 125): no hemolysis;
Tube No. 5 (Todd unit 166): hemolysis
A. Positive Todd unit 125
B. Positive Todd unit 166
C. No antistreptolysin O present
D. Impossible to interpret
A. Positive Todd unit 125
Which control shows the correct result for a valid ASO test?
A. SLO control, no hemolysis
B. Red cell control, no hemolysis
C. Positive control, hemolysis in all tubes
D. Hemolysis in both SLO and red cell control
B. Red cell control, no hemolysis
A streptozyme test was performed, but the result was negative, even though the patient showed clinical signs of a streptococcal throat infection. What should be done next?
A. Either ASO or anti-deoxyribonuclease B (anti-DNase B) testing
B. Another streptozyme test using diluted serum
C. Antihyaluronidase testing
D. Wait for 3-5 days and repeat the streptozyme test
A. Either ASO or anti-deoxyribonuclease B (anti-DNase B) testing
Rapid assays for influenza that utilize specimens obtained from nasopharyngeal swabs detect:
A. IgM anti-influenza
B. IgA anti-influenza
C. IgA-influenza Ag immune complexes
D. Influenza antigen
D. Influenza antigen
How can interfering cold agglutinins be removed from a test sample?
A. Centrifuge the serum and remove the top layer
B. Incubate the clot at 1°C-4°C for several hours, then remove serum
C. Incubate the serum at 56°C in a water bath for 30 minutes
D. Use an anticoagulated sample
B. Incubate the clot at 1°C-4°C for several hours, then remove serum
All tubes (dilutions) except the negative control are positive for cold agglutinins. This indicates:
A. Contaminated red cells
B. A rare antibody against red cell antigens
C. The sample was stored at 4°C prior to separating serum and cells
D. Further serial dilution is necessary
D. Further serial dilution is necessary
All positive cold agglutinin tubes remain positive after 37°C incubation except the positive control. What is the most likely explanation for this situation?
A. High titer cold agglutinins
B. Contamination of the test system
C. Antibody other than cold agglutinins
D. Faulty water bath
C. Antibody other than cold agglutinins
Which increase in antibody titer (dilution) best indicates an acute infection?
A. From 1:2 to 1:8
B. From 1:4 to 1:16
C. From 1:16 to 1:256
D. From 1:64 to 1:128
C. From 1:16 to 1:256
Which of the following positive antibody tests may be an indication of recent vaccination or early primary infection for rubella in a patient with no clinical symptoms?
A. Only IgG antibodies positive
B. Only IgM antibodies positive
C. Both IgG and IgM antibodies positive
D. Fourfold rise in titer for IgG antibodies
B. Only IgM antibodies positive
Why is laboratory diagnosis difficult in cases of Lyme disease?
A. Clinical response may not be apparent upon initial infection; IgM antibody may not be detected until 3-6 weeks after the infection
B. Laboratory tests may be designed to detect whole Borrelia burgdorferi, not flagellar antigen found early in infection
C. Most laboratory tests are technically demanding and lack specificity
D. Antibodies formed initially to B. burgdorferi may cross react in antigen tests for autoimmune diseases
A. Clinical response may not be apparent upon initial infection; IgM antibody may not be detected until 3-6 weeks after the infection
Serological tests for which disease may give a false-positive result if the patient has Lyme disease?
A. AIDS
B. Syphilis
C. Cold agglutinins
D. Hepatitis C
B. Syphilis
In monitoring an HIV-infected patient, which parameter may be expected to be the most sensitive indicator of the effectiveness of antiretroviral treatment?
A. HIV antibody titer
B. CD4:CD8 ratio
C. HIV viral load
D. Absolute total T-cell count
C. HIV viral load
A renal transplant recipient is found to have a rising creatinine level and reduced urine output. The physician orders a “Urine PCR” assay. When you call to find out what organism the physician wants to identify, you are told:
A. Hepatitis C virus
B. Legionella pneumophila
C. EBV
D. BK virus
D. BK virus
A newborn is to be tested for a vertically transmitted HIV infection. Which of the following tests is most useful?
A. HIV PCR
B. CD4 count
C. Rapid HIV antibody test
D. HIV IgM antibody test
A. HIV PCR
Which of the following methods used for HIV identification is considered a signal amplification technique?
A. Branched chain DNA analysis
B. DNA PCR
C. Reverse transcriptase PCR
D. Nucleic acid sequence based assay (NASBA)
A. Branched chain DNA analysis
Which of the following fungal organisms is best diagnosed by an antibody detection test as opposed to an antibody detection assay?
A. Histoplasma
B. Cryptococcus
C. Candida
D. Aspergillus
B. Cryptococcus
Your cytology laboratory refers a Papanicolaou smear specimen to you for an assay designed to detect the presence of a virus associated with cervical cancer. You perform:
A. An ELISA assay for anti-HSV-2 antibodies
B. A molecular assay for HSV-2
C. An ELISA assay for HPV antibodies
D. A molecular assay for HPV
D. A molecular assay for HPV
An immunosuppressed patient has an unexplained anemia. The physician suspects a parvovirus B19 infection. A parvovirus IgM test is negative. The next course of action is to tell the physician:
A. The patient does not have parvovirus
B. A convalescent specimen is recommended in 4 weeks to determine if a fourfold rise in titer has occurred
C. A parvovirus PCR is recommended
D. That a recent transfusion for the patient’s anemia may have resulted in a false-negative assay and the patient should be retested in 4 weeks
C. A parvovirus PCR is recommended
