Deck 11: Labeled Immunoassays

Question 1

A good enzyme for use in an immunoassay should have a:

A) rapid degradation rate.
B) high substrate conversion rate.
C) high cost.
D) toxic enzymatic product.

Answer 1

high substrate conversion rate.

Question 2

Which assay format is the best choice for measuring small molecules,such as drugs and small peptide hormones?

A) Latex agglutination
B) Fluorescence polarization
C) Capture ELISA

Answer 2

Fluorescence polarization

Question 3

An ELISA assay was performed on a patient's serum sample.What is the relationship of the amount of enzyme activity to the amount of patient analyte measured?

A) Directly proportional
B) Indirectly proportional

Answer 3

Directly proportional

Question 4

Compared to a heterogeneous assay,a homogeneous assay:

A) is more sensitive.
B) requires more procedural steps.
C) is easier to adapt to automation.
D) is more specific.

Question 5

In which of the following testing situations is there a direct relationship between the amount of bound label and the amount of patient antigen present?

A) Competitive radioimmunoassay using labeled antigen
B) Competitive enzyme immunoassay using labeled antigen
C) Noncompetitive enzyme immunoassay using a second labeled antibody
D) Any of the above

Question 6

A tissue section is fixed to a microscope slide,then incubated with a fluorescently labeled antibody that binds to an antigen expressed by cells in that tissue.The preparation is then washed and inspected with a fluorescent microscope.This technique is called:

A) direct immunofluorescence.
B) indirect immunofluorescence.
C) fluorescence polarization.
D) autofluorescence.

Question 7

Which statement about noncompetitive enzyme immunoassays is true?

A) Binding sites for patient antigen are limited.
B) Washing in between steps is not necessary.
C) All patient antigen is allowed to react with binding sites.
D) Color is indirectly proportional to the concentration.

Question 8

An immunoassay is performed in the following way: Antigen is bound to a solid support.Patient serum is added,and patient antibodies bind to the antigen.The well is washed,and enzyme-labeled anti-immunoglobulin antibodies are added.The well is washed,and enzyme substrate is added.Enzyme activity is determined.Which immunoassay is described?

A) Capture
B) Competitive
C) ELISA
D) Homogeneous

Question 9

In a capture assay to determine the presence of a viral antigen in a patient sample,which of the following would be on solid phase?

A) Antigen
B) Labeled antibody
C) Unlabeled antibody
D) Antihuman immunoglobulin

Question 10

You must choose between two widely accepted,commonly used colorimetric enzyme immunoassay kits to measure a plasma protein that circulates at a moderately high concentration.Each kit uses a different enzyme and substrate.What is the most important consideration in making your choice?

A) Shelf life of reagents
B) Speed of detection
C) Wavelengths detected by microtiter plate reader
D) Sensitivity

Question 11

An immunoassay is performed in the following manner to look for an antigen (Ag)in the patient serum: Patient serum + labeled Ag + known antibody (Ab)are added together and incubated.Unbound material is washed off.The amount of labeled Ag is then measured.What assay is performed?

A) Homogeneous
B) Competitive
C) Capture
D) ELISA

Question 12

Point-of-care testing is performed most easily using:

A) homogeneous enzyme immunoassay.
B) immunofixation assay.
C) immunochromatographic assay.
D) capture ELISA.

Question 13

In the following equation,what is the ratio of bound radioactive (*)antigen to bound patient antigen (w:x)??8Ag* + 4Ag + 6Ab ---> (w)Ag*Ab + (x)AgAb + (y)Ag* + (z)Ag

A) 1:6
B) 1:3
C) 2:1
D) 8:6

Question 14

Which of the following best describes homogeneous assays?

A) A washing step is not necessary.
B) The concentration of patient antigen is always directly proportional to the label detected.
C) The reagent antibody has an enzyme tag.
D) Labeled and unlabeled analyte are present in equal amounts.

Question 15

Identify the characteristic associated with noncompetitive enzyme immunoassays.

A) They are less sensitive than agglutination reactions.
B) They are used when quantitation is necessary.
C) Antibody is bound to the solid phase.
D) Binding sites for patient antibody are limited.

Question 16

Compared with a capture assay,a radioimmunoassay is likely to be more advantageous in terms of:

A) use in diverse, nonlaboratory settings.
B) cost of equipment.
C) detecting small molecules.
D) cost of reagents.

Question 17

In the following equation,what is the ratio of free radioactive (*)antigen to free patient antigen (the ratio of y/z)after addition of the antibody and after all reactants have reached equilibrium??10 Ag* + 5 Ag + 3 Ab ---> (w)Ag*Ab + (x)AgAb + (y)Ag* + (z)Ag

A) 2:1
B) 1:2
C) 3:1
D) 5:1

Question 18

Indirect immunofluorescence is similar to which type of enzyme immunoassay in terms of the performance of the assay?

A) Competitive
B) Capture
C) ELISA
D) Homogeneous

Question 19

Which of the following best describes competitive binding assays?

A) A limited number of binding sites are present.
B) The concentration of patient antigen is directly proportional to the label detected.
C) All patient antigen present is allowed to bind.
D) Labeled and unlabeled analyte are present in equal amounts.

Question 20

An antigen is fixed to a microscope slide,then incubated with patient serum.After washing,fluorescently labeled anti-human immunoglobulin is applied.After an additional wash,the slide is inspected with a fluorescent microscope.This technique is called:

A) direct immunofluorescence.
B) indirect immunofluorescence.
C) fluorescence polarization.
D) autofluorescence.

Question 21

Which assay format has the lowest equipment cost?

A) Enzyme immunoassay
B) Immunochromatography
C) Fluorescence polarization
D) Chemiluminescence

Question 22

Extremely high analyte concentrations can cause false-negative results (hook effect)in which type of assay?

A) Homogeneous competitive
B) Heterogeneous competitive
C) Homogeneous noncompetitive
D) Heterogeneous noncompetitive

Question 23

Which compound would be an appropriate label in a chemiluminescent assay?

A) Horseradish peroxidase
B) Iodine-125
C) Fluorescein
D) Ruthenium derivative

Question 24

Which assay poses the greatest risk of exposure to biohazards?

A) Radioimmunoassay
B) Enzyme immunoassay
C) Fluorescence polarization
D) Chemiluminescent immunoassays

Question 25

The standard method for detecting antinuclear antibodies (in certain autoimmune diseases)is:

A) direct immunofluorescence.
B) indirect immunofluorescence.
C) fluorescence polarization.
D) autofluorescence.

Question 26

The signal measured in a fluorescence polarization immunoassay is the:

A) wavelength of absorbed light.
B) angle of light scattering.
C) intensity of light emission.
D) orientation of emitted light waves.

Question 27

Pregnancy testing can be performed at home using:

A) capture assay.
B) immunochromatography.
C) fluorescence polarization.
D) chemiluminescence.

Question 28

Select the technique that would most likely be used to determine the concentration of a therapeutic drug.

A) Radioimmunoassay
B) Chemiluminescent assay
C) Fluorescence polarization immunoassay
D) Enzyme immunoassay

Question 29

Quenching of the signal emitted by the label is of particular concern in:

A) radioimmunoassay.
B) enzyme immunoassay.
C) fluorescence polarization.
D) chemiluminescent immunoassays.

Question 30

Rheumatoid factor can cause false-positive results in which type of assay?

A) Homogeneous competitive
B) Heterogeneous competitive
C) Homogeneous noncompetitive
D) Heterogeneous noncompetitive