Test Bank For Immunology and Serology in Laboratory Medicine 6th Edition by Turgeon
Test Bank For Immunology and Serology in Laboratory Medicine 6th Edition by Turgeon
Test Bank For Immunology and Serology in Laboratory Medicine 6th Edition by Turgeon
MULTIPLE CHOICE
5. All the following procedures are typically performed by latex agglutination or latex
agglutination inhibition assays except
a. C-reactive protein (CRP).
b. rheumatoid factors (IgG).
c. pregnancy testing.
d. RPR for syphilis.
ANS: D
The following immunologic assays are performed by latex particle agglutination:
• Latex agglutination—CRP, IgG and IgM rheumatoid factors, rubella antibody
• Latex agglutination inhibition—pregnancy testing
In latex agglutination procedures, if an antigen is present in a test specimen (e.g., CRP), the
antigen will bind to the combining sites of the antibody exposed on the surface of the latex
beads, forming visible cross-linked aggregates of latex beads and antigen. In some test
systems (e.g., pregnancy, rubella antibody), latex particles can be coated with antigen. In the
presence of serum antibodies, these particles agglutinate into large, visible bodies.
Flocculation testing can be used in syphilis serologic testing. In the rapid plasma reagin (RPR)
test, the antigen, cardiolipin-lecithin-coated cholesterol with choline chloride, contains
charcoal particles that allow for macroscopically visible flocculation.
7. A false-positive latex agglutination assay for pregnancy can be produced by all the following
except:
a. cross-reactivity with luteinizing hormone (LH).
b. cross-reactivity with follicle-stimulating hormone (FSH).
c. antisperm antibodies.
d. monoclonal antibody directed against the beta subunit of hCG.
ANS: D
False-Positive Results
If a patient has been given an hCG injection (e.g., Profasi, Pregnyl) to trigger ovulation or
lengthen the luteal phase of the menstrual cycle, trace amounts can remain in the patient’s
system for as long as 10 days after the last injection. This will produce a false-positive result.
Two consecutive quantitative hCG blood assays can circumvent this problem. If the hCG
level increases by the second test, the patient is probably pregnant.
Chorioepithelioma, hydatidiform mole, or excessive ingestion of aspirin may yield
false-positive results. In men, a test identical to the one used for pregnancy may be performed
to detect the presence of a testicular tumor. If monoclonal antibody against the beta subunit is
not used, other hormones with the same alpha unit may cross-react and cause a false-positive
reaction.
False-Negative Results
Testing before reaching detectable levels of hCG will yield false-negative results.
11. The lattice hypothesis states that an optimal reaction occurs between antigen and antibody
when
a. an excess of antigen is present.
b. an excess of antibody is present.
c. antigen and antibody are present in approximately equal proportions.
d. reaction takes place at room temperature.
ANS: C
Precipitation reactions depend on a zone of equivalence, the zone in which optimum
precipitation occurs because the number of multivalent sites of antigen and antibody are
approximately equal. For a precipitation reaction to be detectable, the reaction must occur in
the zone of equivalence. In this zone, each antibody or antigen binds to more than one antigen
or antibody, respectively, forming a stable lattice or network.
The lattice hypothesis is based on an assumption that each antibody molecule must have at
least two binding sites, and an antigen must be multivalent.
13. If a slide agglutination test is rotated for less than 1 minute, as the directions specify, what
source of error can occur?
a. Possible false-positive
b. Possible false-negative
c. Depends on the amount of antibody present in the sample
d. No effect on the results
ANS: B
Causes of False-Negative Agglutination Reactions
Inadequate washing of red blood cells in antihuman globulin (AHG) testing may result in
unbound immunoglobulins neutralizing the reagent.
Failure to add AHG reagent.
Contaminated or expired reagents.
Improper incubation.
Delay in reading slide reactions.
Under centrifugation.
Prozone phenomenon.
14. In a group A patient’s reverse serum testing, the cells and serum agglutinate because
a. group A antigen is present on the patient’s erythrocytes.
b. group A antigen is present in the patient’s serum.
c. anti-group A is present in the patient’s serum.
d. Both A and C.
ANS: A
Reactions of Patient Serum and Reagent Erythrocytes
15. In nephelometric methods, the relationship between the protein being assayed (the antigen in
this instance) and the concentration of the protein in the sample (as measured by the
instrument as the amount of scattered light) is
a. inversely proportional.
b. directly proportional.
ANS: B
The procedure is based on the reaction between the protein being assayed and a specific
antiserum. The resulting complexes of insoluble precipitants scatter incident light in solutions.
The amount of scattered light is proportional to the number of insoluble complexes and can be
quantitated by comparing the unknown patient values with standards of known protein
concentration.
18. In nephelometry measurement, if antigen overwhelms the quantity of antibody, the measured
signal
a. increases.
b. decreases.
c. remains the same.
d. fluctuates between high and low.
ANS: B
The relationship between the quantity of antigen and measuring signal at a constant antibody
concentration is expressed by the Heidelberger curve. If antibodies are present to excess, a
proportional relationship exists between the antigen and resulting signal. If the antigen
overwhelms the quantity of antibody, the measured signal decreases.
MATCHING
1. Coagglutination
2. Flocculation
3. Hemagglutination
4. Prozone phenomenon
5. Postzone phenomenon
6. IgM
7. IgG
Match the cause of a false-positive agglutination reaction with the appropriate corrective
measure.
a. Use a control with saline and no antibody.
b. Read reactions exactly as specified.
c. Calibrate centrifuge to proper speed and time.
d. Use positive and negative QC cells.
8. Over centrifugation of cells and serum
9. Autoagglutination
Match the cause of a false-negative agglutination reaction with the appropriate corrective
measure.
Match the grade of the agglutination reaction with the appropriate description.
a. Tiny aggregates
b. No aggregates
c. Medium-sized aggregates, some free red blood cells (RBCs)
d. Clear supernatant
13. Negative
14. Weak ()
15. 2+
16. 4+