Immunology 3.2 Immunologic Procedures Flashcards
The interaction between individual antigen and antibody molecules depends on several types of bonds, such as ionic bonds, hydrogen bonds, hydrophobic bonds, and van der Waals forces. How is the strength of this attraction characterized?
A. Avidity
B. Affinity
C. Reactivity
D. Valency
B. Affinity
A laboratory is evaluating an enzyme-linked immunosorbent assay (ELISA) for detecting an antibody to cyclic citrullinated peptide (CCP), which is a marker for rheumatoid arthritis (RA). The laboratory includes serum from healthy volunteers and from patients with other connective tissue diseases in the evaluation. These specimens determine which factor of the assay?
A. Sensitivity
B. Precision
C. Bias
D. Specificity
D. Specificity
The detection of precipitation reactions depends on the presence of optimal proportions of antigen and antibody. A patient’s sample contains a large amount of antibody, but the reaction in a test system containing antigen is negative. What has happened?
A. Performance error
B. Low specificity
C. A shift in the zone of equivalence
D. Prozone phenomenon
D. Prozone phenomenon
The positive and negative control values for an ELISA procedure are below their acceptable ranges. What is the most likely cause?
A. Decay of the positive and negative controls
B. Incomplete washing following specimen addition
C. Overly long incubation times
D. Decay of the antibody–enzyme conjugate
D. Decay of the antibody–enzyme conjugate
What is the interpretation when an Ouchterlony plate shows crossed lines between wells 1 and 2 (antigen is placed in the center well and antisera in wells 1 and 2)?
A. No reaction between wells 1 and 2
B. Partial identity between wells 1 and 2
C. Nonidentity between wells 1 and 2
D. Identity between wells 1 and 2
C. Nonidentity between wells 1 and 2
A weight lifter taking many supplements is tested monthly for thyroid-stimulating hormone (TSH) in a direct capture assay, which uses a streptavidin–biotin indicator system. She has had normal TSH levels for the past 3 months on specimens collected in the late evening. This month she comes in right after breakfast for her blood draw. The TSH level is three times her previous level. What may be the cause of this difference?
A. Diurnal variation in TSH levels
B. Exogenous biotin in her system from a supplement taken that morning
C. Reduced thyroid function caused by an unidentified pathology
D. Pipetting error
B. Exogenous biotin in her system from a supplement taken that morning
What comprises the indicator system in an indirect ELISA for detecting antibody?
A. Enzyme-conjugated antibody + chromogenic substrate
B. Enzyme conjugated antigen + chromogenic substrate
C. Enzyme + antigen
D. Substrate + antigen
A. Enzyme-conjugated antibody + chromogenic substrate
What outcome results from improper washing of a tube or well after adding the enzyme–antibody conjugate in an ELISA system?
A. Result will be falsely decreased
B. Result will be falsely increased
C. Result will be unaffected
D. Result is impossible to determine
B. Result will be falsely increased
What would happen if the color reaction phase is prolonged in one tube or well of an ELISA test?
A. Result will be falsely decreased
B. Result will be falsely increased
C. Result will be unaffected
D. Impossible to determine
B. Result will be falsely increased
The absorbance of a sample measured by ELISA is greater than the highest standard. What corrective action should be taken?
A. Extrapolate an estimated value from the highest reading
B. Repeat the test using a standard of higher concentration
C. Repeat the assay using one half the volume of the sample
D. Dilute the test sample
D. Dilute the test sample
A patient was suspected of having a lymphoproliferative disorder. After several laboratory tests were completed, the patient was found to have an IgMκ paraprotein. In what sequence should the laboratory tests leading to this diagnosis have been
performed?
A. Serum protein electrophoresis (SPE) followed by immunofixation electrophoresis (IFE)
B. Ig levels, followed by SPE
C. Total lymphocyte count, followed by Ig levels
D. Ig levels, followed by urine protein electrophoresis
A. Serum protein electrophoresis (SPE) followed by immunofixation electrophoresis (IFE)
An IFE performed on a serum sample showed a narrow dark band in the lanes
containing anti-γ and anti-λ. How should this result be interpreted?
A. Abnormally decreased IgG concentration
B. Abnormal test result demonstrating monoclonal IgGλ
C. Normal test result
D. Impossible to determine without densitometric quantitation
B. Abnormal test result demonstrating monoclonal IgGλ
Which type of nephelometry is used to measure immune complex formation almost immediately after reagent has been added?
A. Rate
B. Endpoint
C. Continuous
D. One-dimensional
A. Rate
An antinuclear antibody (ANA) test was performed by using immunofluorescence microscopy assay (IFA), and a clinically significant pattern and titer were reported. Positive and negative controls performed as expected. However, the clinical evaluation of the patient was not consistent with the reported pattern. What is the most likely explanation for this situation?
A. The clinical condition of the patient changed since the sample was tested
B. The pattern of fluorescence was misinterpreted
C. The control results were misinterpreted
D. The wrong cell line was used for the test
B. The pattern of fluorescence was misinterpreted
What corrective action should be taken when a specific pattern cannot be identified in a specimen with a positive ANA IFA?
A. Repeat the test using a larger volume of sample
B. Call the physician
C. Have another medical laboratory scientist read the slide
D. Dilute the sample and retest
D. Dilute the sample and retest
