STUDY Q’S Flashcards
- Which of the following statements accurately
describes competitive binding assays?
a. Excess binding sites for the analyte are provided
b. Labeled and unlabeled analyte are present in
equal amounts.
c. The concentration of patient analyte is inversely
proportional to bound label.
d. All the patient analyte is bound in the reaction.
c. The concentration of patient analyte is inversely proportional to bound label.
- How do heterogeneous assays ditter from homogeneous assays?
a. Heterogeneous assays require a separation step.
b. Heterogeneous assays are easier to perform than
homogeneous assays.
c. The concentration of patient analyte is indirectly
proportional to bound label in heterogeneous
assays.
d. Homogeneous assays are more sensitive than
heterogeneous ones.
a. Heterogeneous assays require a separation step.
In the following equation, what is the ratio of
bound radioactive antigen (Ag*) to bound patient antigen (Ag)?
12Ag* + 4Ag + 4Ab → :_ Ag*
Ab + AgAb + Ag*+ Ag
a. 1:4
b. 1:3
c. 3:1
d. 8:4
c. 3:1
Which of the following responses characterizes a
capture or sandwich enzyme assay?
a. Less sensitive than competitive enzyme assays
b. Requires two wash steps
c. Best for small antigens with a single determinant
d. A limited number of antibody sites on solid phase
b. Requires two wash steps
- Which of the following is an advantage of enzyme immunoassay over RIA?
a. Decrease in hazardous waste
b. Shorter shelf life of kit
c. Natural inhibitors do not affect results
d. Needs to be read manually
a. Decrease in hazardous waste
Which of the following is characteristic of direct
fluorescent assays?
a. The anti-immunoglobulin has the fluorescent tag.
b. Antibody is attached to a solid phase.
c. Microbial antigens can be rapidly identified by
this method
d. The amount of color is in inverse proportion to the
amount of antigen present.
c. Microbial antigens can be rapidly identified by
this method.
Which of the following is true of fluorescence polarization immunoassay?
a. Both antigen and antibody are labeled
b. Large molecules polarize more light than smaller molecules.
c. When binding occurs, there is quenching of the fluorescent tag.
d. The amount of fluorescence is directly proportional to concentration of the analyte.
b. Large molecules polarize more light than smaller molecules.
A fluorescent substance is best described as one in which
a. light energy is absorbed and converted to a longer wavelength.
b. the emitted wavelength can be seen under normal white light.
c. there is a long time between the absorption and emission of light.
d. it spontaneously decays and emits light.
a. light energy is absorbed and converted to a longer wavelength.
In a noncompetitive enzyme immunoassay, if a negative control shows the presence of color, which of the following might be a possible explanation?
a. No reagent was added.
b. Washing steps were incomplete.
c. The enzyme was inactivated.
d. No substrate was present.
b. Washing steps were incomplete.
Which of the following best characterizes chemiluminescent assays?
a. Only the antigen can be labeled.
b. Tests can be read manually.
c. These are only homogeneous assays.
d. A chemical is oxidized to produce light.
d. A chemical is oxidized to produce light.
Immunofluorescent assays may be difficult to interpret for which reason?
a. Autofluorescence of substances in serum
b. Nonspecific binding to serum proteins
c. Subjectivity in reading results
d. Any of the above
d. Any of the above
Which statement best describes flow-through
immunoassays?
a. Results are quantitative.
b. They are designed for point-of-care testing.
c. Reagents must be added separately.
d. They are difficult to interpret.
b. They are designed for point-of-care testing.
- Which of the following is characteristic of an indirect enzyme immunoassay?
a. The first antibody has the enzyme label.
b. All reagents are added together.
c. Color is directly proportional to the amount of
patient antigen present.
d. Enzyme specificity is not essential.
c. Color is directly proportional to the amount of
patient antigen present.
In a homogeneous enzyme immunoassay, which best describes the enzyme?
a. Enzyme activity is altered when binding to antibody occurs.
b. The enzyme label is on the antibody.
c. Enzyme activity is directly proportional to the
amount of patient antigen present.
d. Most enzymes can be used in this type of assay.
c. Enzyme activity is directly proportional to the
amount of patient antigen present.
In an indirect immunofluorescent assay, what
would be the outcome of an improper wash after the antibody-enzyme conjugate is added?
a. Results will be falsely decreased.
b. Results will be falsely increased.
c. Results will be unaffected.
d. It would be difficult to determine the effect.
b. Results will be falsely increased.
In a heterogeneous enzyme immunoassay, if the
patient sample produces more color than the highest positive control, what action should be taken?
a. Report the results out as determined.
b. Dilute the patient sample.
c. Repeat the assay using one-half the volume of the patient sample.
d. Report the results as falsely positive.
b. Dilute the patient sample.
All of the following are protective mechanisms against bacteria except
a. production of antimicrobial defense peptides.
b. phagocytosis.
c. activation of complement.
d. release of lipid A from the bacterial cell.
d. release of lipid A from the bacterial cell.
All of the following are characteristics of streptococcal M proteins except
a. it is the chief virulence factor of Group A
streptococci.
b. it provokes an immune response.
c. antibodies to one serotype protect against other serotypes.
d. it limits phagocytosis of the organism.
c. antibodies to one serotype protect against other serotypes.
An ASO titer and a streptozyme test are performed on a patient’s serum. The ASO titer is negative, the streptozyme test is positive, and both the positive and negative controls react appropriately. What can you conclude from these test results?
a. The ASO is falsely negative.
b. The patient has an antibody to a streptococcal
exoenzyme other than streptolysin O.
c. The patient has not had a previous streptococcal infection.
d. The patient has scarlet fever.
b. The patient has an antibody to a streptococcal
exoenzyme other than streptolysin O.
Which of the following applies to acute rheumatic fever?
a. Symptoms begin after S. pyogenes infection of the throat or the skin.
b. Antibodies to Group A streptococci are believed to cross-react with heart tissue.
c. Diagnosis is usually made by culture of the organism.
d. All patients suffer permanent disability.
b. Antibodies to Group A streptococci are believed to cross-react with heart tissue.
Which of the following indicates the presence of anti-DNase B activity in serum?
a. Reduction of methyl green from green to colorless
b. Clot formation when acetic acid is added
c. Inhibition of red blood cell hemolysis
d. Lack of change in the color indicator
a. Reduction of methyl green from green to colorless
Which of the following is considered to be a nonsuppurative complication of streptococcal infection?
a. Acute rheumatic fever
b. Scarlet fever
c. Impetigo
d. Pharyngitis
a. Acute rheumatic fever
All of the following are ways that bacteria can evade host defenses except
a. presence of a capsule.
b. stimulation of chemotaxis.
c. production of toxins.
d. lack of adhesion to phagocytic cells.
b. stimulation of chemotaxis.
Antibody testing for Rocky Mountain spotted fever may not be helpful for which reason?
a. It is not specific.
b. It is too complicated to perform.
c. It is difficult to obtain a blood specimen.
d. Antibody production takes at least a week before
detection.
d. Antibody production takes at least a week before detection.
Which of the following enzymes is used to detect the presence of H pylori infections?
a. DNase
b. Hyaluronidase
c. Urease
d. Peptidase
c. Urease
Which of the following reasons make serological identification of a current infection with Helicobacter pylori difficult?
a. No antibodies appear in the blood.
b. Only IgM is produced.
c. Antibodies remain after initial treatment.
d. No ELISA tests have been developed.
c. Antibodies remain after initial treatment.
M pneumoniae infections are associated with the production of which antibodies?
a. Cold agglutinins
b. Antibodies to ATPase
c. Antibodies to DNase
d. Antibodies to Proteus bacteria
a. Cold agglutinins
Which of the following best describes the principle of
the IFA test for detection of antibodies produced in
Rocky Mountain spotted fever?
Specific antibodies in the serum sample attach to the antigens fixed to a microscope slide. In a second step, the attached antibodies are stained withfluorescein-labeled anti-human immunoglobulin and visualized with the fluorescence microscope.
Which of the following is true regarding exotoxins and endotoxins?
Endotoxin is released from the cell wall of dead
bacteria, whereas exotoxin is released from live
bacteria.
Characteristics of a bacterial capsule include which of the following?
a. It cannot be used for vaccine development.
b. It is composed of peptidoglycan.
c. It is an important mechanism for protecting a
bacterium against ingestion by PMNs.
d. It is what causes bacteria to stain as gram-negative.
c. It is an important mechanism for protecting a
bacterium against ingestion by PMNs.
Which of the following statements regarding Helicobacter pylori is not true?
a. It is associated with an increased risk of gastric
carcinoma.
b. It is the cause of most cases of acute food poisoning in the United States.
c. It is a major cause of peptic ulcers in the United States.
d. It is positive for urease.
b. It is the cause of most cases of acute food poisoning in the United States.
False-positive nontreponemal tests for syphilis may occur because of which of the following?
a. Infectious mononucleosis
b. Systemic lupus
c. Pregnancy
d. All of the above
d. All of the above
In the fluorescent treponemal antibody absorption (FTA-ABS) test, what is the purpose of absorption with Reiter treponemes?
a. It removes reactivity with lupus antibody.
b. It prevents cross-reactivity with antibody to other T pallidum subspecies.
c. It prevents cross-reactivity with antibody to
nonpathogenic treponemes.
d. All of the above.
c. It prevents cross-reactivity with antibody to
nonpathogenic treponemes.
Which test is recommended for testing cerebrospinal fluid for detection of neurosyphilis?
a. RPR
b. VDRL
c. FTA-ABS
d. Enzyme immunoassay
b. VDRL
Advantages of direct fluorescent antibody testing to T pallidum include all of the following except
a. reading is less subjective than with dark-field
testing.
b. monoclonal antibody makes the reaction very
specific.
c. slides can be prepared for later reading.
d. careful specimen collection is less important than in dark-field testing.
d. careful specimen collection is less important than in dark-field testing.
Which of the following is true of nontreponemal
antibodies?
k
a. They can be detected in all patients with primary syphilis.
b. These antibodies are directed against cardiolipin
c. Nontreponemal tests remain positive after
successful treatment.
d. The antibodies are only found in patients with
syphilis.
b. These antibodies are directed against cardiolipin.
Which of the following is true of treponemal tests for syphilis?
a. They are usually negative in the primary stage.
b. Titers decrease with successful treatment.
c. In large-volume testing, they are often used as
screening tests.
d. They are subject to a greater number of false positives than nontreponemal tests.
c. In large-volume testing, they are often used as
screening tests.
An RPR test done on a 19-year-old woman as part of a prenatal workup was negative but exhibited a rough appearance. What should the technologist do next?
a. Report the result out as negative.
b. Do a VDRL test.
c. Send the sample for confirmatory testing.
d. Make serial dilutions and do a titer.
Make serial dilutions and do a titer.
Treponemal ElA tests for syphilis are characterized by all of the following except
a. they are adaptable to automation.
b. they are useful in monitoring antibody titers in
syphilis patients undergoing therapy.
c. subjectivity in reading is eliminated.
d. they can be used to distinguish between IgG and IgM antibodies.
they are useful in monitoring antibody titers in
syphilis patients undergoing therapy.
Which of the following tests is the most specific
during the early phase of Lyme disease?
a. IFA
b. EIA
c. Immunoblotting
d. detection of B burgdorferi DNA by PCR
d. detection of B burgdorferi DNA by PCR
False-positive serological tests for Lyme disease may be caused by all of the following except
a. shared antigens between Borrelia groups.
b. cross-reactivity of antibodies.
c. resemblance of flagellar antigen to that of
Treponema organisms.
d. a patient in the early stage of the disease.
d. a patient in the early stage of the disease.
A 24-year-old man who had just recovered from
infectious mononucleosis had evidence of a genital lesion. His RPR test was positive. What should the technologist do next?
a. Report out as false positive.
b. Do a confirmatory treponemal test.
c. Do a VDRL
d. Have the patient return in 2 weeks for a repeat test.
b. Do a confirmatory treponemal test.
A 15-year-old girl returned from a camping trip.
Approximately a week after her return, she
discovered a small red area on her leg that had
a larger red ring around it. Her physician had her
tested for Lyme disease, but the serological test
was negative. What is the best explanation for
these results?
a. She definitely does not have Lyme disease.
b. The test was not performed correctly.
c. Antibody response is often below the level of
detection in early stages.
d. Too much antibody was present, causing a false negative.
c. Antibody response is often below the level of
detection in early stages.
The reverse screening algorithm for syphilis testing
a. is the CDC preferred algorithm.
b. is more labor intensive than the “traditional” method
c. has a high number of false positives that must be resolved by doing a TP-PA test.
d. is more prone to transcription errors in reporting.
c. has a high number of false positives that must be resolved by doing a TP-PA test.
Borrelia miyamotoi infection
a. may explain some cases of supposed Lyme disease
where no rash was tound
b. is a new lethal tick-borne disease.
c. is carried by the common dog tick.
d. is another name for Southern Tick Associated
Illness (STARI).
a. may explain some cases of supposed Lyme disease
where no rash was found
The role of CLs in immune responses against
viruses is to
a. neutralize viral activity.
b. promote destruction of viruses by
ADCC.
c. destroy virus-infected host cells.
d. attack free virions.
c. destroy virus-infected host cells.
Viruses can escape immune detenses by
a. undergoing frequent genetic
mutations.
b. suppressing the immune system.
c. integrating their nucleic acid into the host
genome.
d. all of the above.
d. all of the above.
A patient who has developed immunity to a viral
infection would be expected to have which of the following serology results?
a. IgM+, IgG-
b. IgM-, IgG+
c. IgM+, IgG+
d. IgM-, IgG-
b. IgM-, IgG+
A newborn suspected of having a congenital viral
infection should be tested for virus-specific antibodies of which class(es)?
a. IgM
b. IgG
c. IgA
d. All of the above classes
a. IgM
Which of the following hepatitis viruses is transmitted by the fecal-oral route?
a. Hepatitis B
b. Hepatitis C
c. Hepatitis D
d. Hepatitis E
d. Hepatitis E
An individual with hepatomegaly, jaundice, and
elevated liver enzymes has the following laboratory results:
1gM anti-HAV (negative), HBAg (positive),
IgM anti-HBc (positive), and anti-HCV (negative).
These findings support a diagnosis of
a. hepatitis A
b. acute hepatitis B.
c. chronic hepatitis B.
d. hepatitis C
b. acute hepatitis B
The serum of an individual who received all doses of the hepatitis B vaccine should contain
a. anti-HBs.
b. anti-HBe.
c. anti-HBc.
I. all of the above.
a. anti-HBs.
Quantitative tests for HCV RNA are used to
a. screen for hepatitis C.
b. determine the HCV genotype.
c. differentiate acute HCV infection from chronic
HCV infection.
d. monitor hepatitis C patients on antiviral therapy.
d. monitor hepatitis C patients on antiviral therapy.
In the laboratory, heterophile antibodies are routinely detected by their reaction with
a. B lymphocytes.
b. bovine erythrocyte antigens.
c. sheep erythrocyte antigens.
d. Epstein-Barr virus antigens.
b. bovine erythrocyte antigens.
The presence of IgM anti-rubella antibodies in the serum from an infant born with a rash suggests
a. a diagnosis of measles.
b. a diagnosis of German measles.
c. congenital infection with the rubella virus.
d. passive transfer of maternal antibodies to the
infant’s serum.
c. congenital infection with the rubella virus.
A pregnant woman is exposed to a child with a
rubella infection. She had no clinical symptoms but had a rubella titer performed. Her antibody titer was 1:8. Three weeks later, the test was repeated and her titer was 1:128. She still had no clinical symptoms.
Was the laboratory finding indicative of rubella
infection?
a. No, the titer must be greater than 256 to be
significant.
b. No, the change in titer is not significant if no
clinical signs are present.
c. Yes, a greater than four-fold rise in titer indicates early infection.
d. Yes, but clinical symptoms must also correlate
with laboratory findings.
c. Yes, a greater than four-fold rise in titer indicates early infection.
The cause of shingles is the
a. cytomegalovirus.
b. rubella virus.
c. varicella-zoster virus.
d. HTLV-I.
C. varicella-zoster virus.
The method of choice for detecting VZV infection
in immunocompromised hosts is
a. serology to detect virus-specific IgM antibodies.
b. serology to detect virus-specific IgG antibodies.
c. viral culture.
d. real-time PCR
d. real-time PCR.
Which of the following is true regarding laboratory testing for mumps?
a. RT-PCR is recommended as the primary
diagnostic test.
b. Serology is necessary for confirmation of a suspected clinical case.
c. IgM tests for mumps are highly specific.
d. An acute infection must be confirmed by a four-fold rise in IgG titer.
RT-PCR is recommended as the primary
diagnostic test.
A positive result on a screening test for HTLV-1 antibody should be
a. considered highly specific for HTLV-I infection.
b. followed by PCR
c. confirmed by Western blot.
d. validated by viral culture.
c. confirmed by Western blot.
All of the following describe HIV except
a. it possesses an outer envelope.
b. it contains an inner core with p24 antigen.
c. it contains DNA as its nucleic acid.
d. it is a member of the retrovirus family.
c. it contains DNA as its nucleic acid
HIV virions bind to host I cells through which
receptors?
a. CD4 and CD8
b. CD4 and the IL-2 receptor
C. CD4 and CCR5
d. CD8 and CCR2
c. CD4 and CCR5
Antibodies to which of the following viral
antigens are usually the first to be detected in
HIV infection?
a. gp 120
b. gp160
c. gp41
d. p24
d. p24
Which of the following is typical of the latent stage of HIV infection?
a. Proviral DNA is attached to cellular DNA.
b. Large numbers of viral particles are synthesized.
c. A large amount of viral RNA is synthesized
d. Viral particles with no envelope are produced.
a. Proviral DNA is attached to cellular DNA
The decrease in T-cell numbers in HIV-infected
individuals is caused by
a. lysis of host I cells by replicating virus.
b. fusion of the T cells to form syncytia.
c. killing of the I cells by HIV-specific cytotoxic I cells.
d. all of the above.
d. all of the above.
The most common means of HIV transmission
worldwide is through
a. blood transfusions.
b. intimate sexual contact.
c. sharing of needles in intravenous drug use.
d. transplacental passage of the virus.
b. intimate sexual contact.
The drug zidovudine is an example of a
a. nucleoside analogue reverse-transcriptase inhibitor.
b. nonnucleoside reverse-transcriptase inhibitor.
c. protease inhibitor.
d. fusion inhibitor.
nucleoside analogue reverse-transcriptase inhibitor.
False-negative test results in a laboratory test for HIV antibody may occur because of
a. heat inactivation of the serum before testing.
b. collection of the test sample before seroconversion.
c. interference by autoantibodies.
d. recent exposure to certain vaccines.
b. collection of the test sample before seroconversion.
Which of the following combinations of bands would represent a positive Western blot for HIV antibody?
a. p24 and p55
b. p24 and p31
c. gp41 and gp 120
d. p31 and p55
c. gp41 and gp 120
The fourth-generation ELISA tests for HIV detect
a. HIV-1 and HIV-2 antigens.
b. HIV-1 and HIV-2 antibodies.
c. p24 antigen.
d. HIV-1 antibodies, HIV-2 antibodies, and p24 antigen
d. HIV-1 antibodies, HIV-2 antibodies, and p24 antigen.
The conjugate used in the fourth-generation ELISA tests for HIV consists of enzyme-labeled
a. anti-human immunoglobulin.
b. HIV-1- and HIV-2-specitic antibodies.
c. HIV-1- and HIV-2-specific antigens.
d. HIV-1- and HIV-2-specific antigens plus antibody
to p24.
d. HIV-1- and HIV-2-specific antigens plus antibody to p24
The characteristic laboratory finding in HIV
infection is
a. decreased numbers of CD4 T cells.
b. decreased numbers of CD8 T cells.
c. decreased numbers of CD20 B cells.
d. decreased immunoglobulins.
a. decreased numbers of CD4 T cells.
Which of the following tests is currently recommended by the CDC to confirm a positive screening test result for HIV infection?
a. Rapid test for HIV-1 and HIV-2 antibodies
b. Western blot
c. Molecular testing for HIV RNA
d. HIV viral culture
a. Rapid test for HIV-1 and HIV-2 antibodies
Which of the following tests would give the least
reliable results in a 2-month-old infant?
a. CD4 T-cell count
b. ELISA for HIV antibody
c. PCR for HIV proviral DNA
d. n24 antigen
b. ELISA for HIV antibody
Which of the following measurements are routinely used to monitor patients with HIV infection who are undergoing antiretroviral therapy?
a. HIV antibody titer
b. p24 antigen levels
c. CD4 T-cell and CD8 T-cell counts
d. CD4 T-cell count and HIV RNA copy number
d. CD4 T-cell count and HIV RNA copy number
