CHAPTER 11: Labeled Immunoassays 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 differ 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.
