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*Chemistry Extern > 3.3 Infectious Diseases > Flashcards

3.3 Infectious Diseases Flashcards

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1
Q

Which serum antibody response usually characterizes the primary (early) stage of syphilis?
A. Antibodies against syphilis are undetectable
B. Detected 1 to 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

A

B. Detected 1 to 3 weeks after appearance of the primary chancre

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2
Q

What substance is detected in the sample by the rapid plasma reagin (RPR) and Venereal Disease Research Laboratory (VDRL) tests for syphilis?
A. Cardiolipin
B. Anticardiolipin antibody (ACA)
C. Anti–Treponema pallidum antibody
D. T. pallidum

A

B. Anticardiolipin antibody (ACA)

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3
Q

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

A

C. Cardiolipin

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4
Q

Which of the following is the most sensitive test to detect congenital syphilis?
A. VDRL
B. RPR
C. T. pallidum particle agglutination (TP-PA)
D. Polymerase chain reaction (PCR)

A

D. Polymerase chain reaction (PCR)

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5
Q

A biological false-positive reaction is least likely with which test for syphilis?
A. VDRL
B. TP-PA
C. RPR
D. All are equally likely to yield a false-positive result

A

B. TP-PA

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6
Q

A 12-year old girl has symptoms of fatigue and localized lymphadenopathy. Laboratory tests reveal peripheral blood lymphocytosis, positive RPR, and positive spot test for IM. What test should be performed next?
A. HIV screen
B. VDRL
C. Epstein-Barr virus (EBV)–specific antigen test
D. TP-PA test

A

D. TP-PA test

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7
Q

Which test is most likely to be positive in the tertiary stage of syphilis?
A. Treponemal-specific antibody
B. RPR
C. VDRL
D. Reagin screen test (RST)

A

A. Treponemal-specific antibody

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8
Q

What is the most likely interpretation of the following syphilis serological results?
RPR: reactive; TP-PA: nonreactive
A. Neurosyphilis
B. Secondary syphilis
C. Syphilis that has been successfully treated
D. Biological false positive

A

D. Biological false positive

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9
Q

Which specimen is the sample of choice to evaluate latent or tertiary syphilis?
A. Serum sample
B. Chancre fluid
C. Cerebrospinal fluid (CSF)
D. Joint fluid

A

C. Cerebrospinal fluid (CSF)

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10
Q

Interpret the following quantitative RPR test results.
RPR titer: weakly reactive—1:4; reactive—1:8 to 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

A. Excess antibody, prozone effect

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11
Q

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

A

B. Tests for antigens, antibodies, and nucleic acid

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12
Q

Which tests are considered screening tests for HIV?
A. ELISA, chemiluminescent, and rapid antibody tests
B. IFA, Western blot, radioimmunoprecipitation assay
C. Culture, antigen capture assay, DNA amplification
D. Reverse transcriptase and messenger RNA (mRNA) assay

A

A. ELISA, chemiluminescent, and rapid antibody tests

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13
Q

Which tests are the recommended confirmatory tests for HIV?
A. ELISA and rapid antibody tests
B. HIV-1,2 antibody differentiation assays, and qualitative PCR test
C. Culture, antigen capture assay, quantitative PCR
D. Reverse transcriptase and mRNA assay

A

B. HIV-1,2 antibody differentiation assays, and qualitative PCR test

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14
Q

How do fourth- and fifth-generation HIV tests reduce the time from infection to the test becoming positive?
A. They are PCR tests detecting viral RNA
B. They detect p24 antigen in addition to HIV antibody
C. They detect proviral DNA
D. They detect antibodies to more antigens than earlier generations of HIV tests

A

B. They detect p24 antigen in addition to HIV antibody

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15
Q

A woman who has had five pregnancies subsequently tests positive for HIV on a fourth generation assay and is negative on an HIV-1,2 differentiation assay and a follow-up molecular assay. The initial reactivity may be caused by:
A. Possible cross-reaction with herpes or EBV antibodies
B. Interference from medication
C. Cross-reacting antibodies elicited during pregnancy
D. Possible technical error; a repeat specimen should be requested

A

C. Cross-reacting antibodies elicited during pregnancy

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16
Q

Interpret the following results for HIV testing:
Fourth-generation ELISA: positive; repeat ELISA:
positive; HIV 1,2 antibody differentiation assay:
negative; qualitative HIV RNA rtPCR assay: positive
A. False-positive fourth-generation assay
B. False-negative antibody differentiation assay
C. Indeterminate; further testing indicated
D. HIV p24 antigen detected on fourth-generation ELISA

A

D. HIV p24 antigen detected on fourth-generation ELISA

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17
Q

What is the most likely explanation when antibody tests for HIV are negative but the PCR test 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

A

B. Patient is in the “window phase” before antibody production

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18
Q

What criteria constitute the classification system for HIV infection?
A. CD4-positive T-cell count and clinical symptoms
B. Clinical symptoms, condition, duration, and strength of reactivity on a fourth-generation HIV test
C. Presence or absence of lymphadenopathy
D. Strong fourth-generation HIV test reactivity and CD8-positive T-cell count

A

A. CD4-positive T-cell count and clinical symptoms

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19
Q

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

A

C. Different strains of the virus are genetically diverse

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20
Q

Which CD4:CD8 ratio is most likely in a patient with AIDS?
A. 2:1
B. 3:1
C. 2:3
D. 1:3

A

D. 1:3

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21
Q

What is the advantage of fourth-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

A

C. They detect p24 antigen

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22
Q

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. PCR test
D. Viral culture

A

C. PCR test

23
Q

What is the most likely cause when a fourth-generation HIV assay is positive for all controls and samples?
A. Improper pipetting
B. Improper washing
C. Improper addition of sample
D. Improper reading

A

B. Improper washing

24
Q

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

A

D. All of these options

25
Q

Which of the following statements regarding infection with hepatitis D virus (HDV) is true?
A. Occurs in patients with HIV infection
B. Does not progress to chronic hepatitis
C. Occurs in patients with hepatitis B virus (HBV) infection
D. Is not spread through blood or sexual contact

A

C. Occurs in patients with hepatitis B virus (HBV) infection

26
Q

All of the following hepatitis viruses are spread through blood or blood products except:
A. Hepatitis A virus (HAV)
B. HBV
C. HCV
D. HDV

A

A. Hepatitis A virus (HAV)

27
Q

Which hepatitis B marker is the best indicator of early acute infection?
A. Hepatitis B surface antigen (HBsAg)
B. Hepatitis B e-antigen (HBeAg)
C. Hepatitis B core antibody (anti-HBc)
D. Hepatitis B surface antibody (anti-HBs)

A

A. Hepatitis B surface antigen (HBsAg)

28
Q

Which is the first antibody detected in serum after infection with HBV?
A. Anti-HBs
B. Anti-HBc IgM
C. Anti-HBe
D. All are detectable at the same time

A

B. Anti-HBc IgM

29
Q

Which antibody persists in low-level carriers of HBV?
A. IgM anti-HBc
B. IgG anti-HBc
C. IgM anti-HBe
D. IgG anti-HBs

A

B. IgG anti-HBc

30
Q

What is the most likely explanation when a patient has clinical signs of viral hepatitis but tests negative for HAV IgM, HBsAg, and HCV antibody?
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

A

C. The patient may be in the “core window”

31
Q

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

A. HBsAg and anti-HBc

32
Q

Which hepatitis antibody confers immunity against reinfection with HBV?
A. Anti-HBc IgM
B. Anti-HBc IgG
C. Anti-HBe
D. Anti-HBs

A

D. Anti-HBs

33
Q

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

A

B. Alanine aminotransferase (ALT)

34
Q

If only anti-HBs is positive, which of the following can be ruled out?
A. HBV vaccination
B. Distant past infection with HBV
C. Hepatitis B immune globulin (HBIG) injection
D. Chronic HBV infection

A

D. Chronic HBV infection

35
Q

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

A

C. Current infection

36
Q

Rapid mono tests use latex particles coated with which of the following?
A. Guinea pig antigen
B. Beef proteins
C. Horse proteins
D. Sheep proteins

A

B. Beef proteins

37
Q

Blood products are tested for which virus before being transfused to newborns?
A. EBV
B. Human T-lymphotropic virus II (HTLV-II)
C. CMV
D. HDV

A

C. CMV

38
Q

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

A

B. Highest serum dilution that shows agglutination

39
Q

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) test
B. Another streptozyme test using diluted serum
C. Antihyaluronidase test
D. Wait for 3 to 5 days and repeat the streptozyme test

A

A. Either ASO or anti-deoxyribonuclease B (anti-DNase B) test

40
Q

Rapid assays for influenza that utilize specimens obtained from nasopharyngeal swabs detect:
A. IgM anti-influenza
B. IgA anti-influenza
C. IgA–influenza antigen immune complexes
D. Influenza nucleoprotein antigens

A

D. Influenza nucleoprotein antigens

41
Q

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 to 4°C for several hours and then remove the serum
C. Incubate the serum at 56°C in a water bath for 30 minutes
D. Use an anticoagulated sample

A

B. Incubate the clot at 1°C to 4°C for several hours and then remove the serum

42
Q

All tubes (dilutions) except the negative control are positive for cold agglutinins. This indicates:
A. Contaminated RBCs
B. A rare antibody against RBC antigens
C. The sample was stored at 4°C prior to separating serum and cells
D. Further serial dilution is necessary

A

D. Further serial dilution is necessary

43
Q

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

A

C. Antibody other than cold agglutinins

44
Q

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

A

C. From 1:16 to 1:256

45
Q

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

A

B. Only IgM antibodies positive

46
Q

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 to 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

A. Clinical response may not be apparent upon initial infection; IgM antibody may not be detected until 3 to 6 weeks after the infection

47
Q

Serological tests for which disease may give a false-positive result if the patient has Lyme disease?
A. HIV
B. Syphilis
C. EBV
D. Hepatitis C

A

B. Syphilis

48
Q

In monitoring a patient with HIV infection, 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

A

C. HIV viral load

49
Q

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. HCV
B. Legionella pneumophila
C. EBV
D. BK virus

A

D. BK virus

50
Q

A newborn is to be tested for 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

A. HIV PCR

51
Q

Which of the following fungal organisms is best diagnosed by an antigen detection test as opposed to an antibody detection assay?
A. Histoplasma
B. Cryptococcus
C. Candida
D. Aspergillus

A

B. Cryptococcus

52
Q

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 for anti-human simplex virus 2 (anti-HSV-2) antibodies
B. A molecular assay for HSV-2
C. An ELISA for human papilloma virus (HPV) antibodies
D. A molecular assay for HPV

A

D. A molecular assay for HPV

53
Q

An immunosuppressed patient has unexplained anemia. The physician suspects a parvovirus B19 infection. The parvovirus IgM test result is negative. The next course of action is to tell the physician that:
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. A recent transfusion for the patient’s anemia may have resulted in a false-negative result and the patient should be retested in 4 weeks

A

C. A parvovirus PCR is recommended

*Chemistry Extern (18 decks)

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