Module 3: Molecular Diagnostics: Practice Questions
1. (D1) A 64 year-old man has recently been prescribed clodipogrel (Plavix) after a recent MI to maintain blood fluidity and to prevent future cardiac events. He recalls, however, that his mother, uncle, and grandmother all took Plavix, and that they experienced some adverse effects, such as excessive bleeding, in the initial course of the drug. Which of the following testing strategies would be most appropriate before dosing this patient for clopidogrel?
A. Complete blood count
B. FISH analysis for the patient's karyotype
C. Probing for the cyp450 2C19 polymorphism
D. Prothrombin time
E. Western blot analysis of blood proteins
Answer: C: Probing for the cyp450 2C19 polymorphism.
Pharmacogenomic testing may reveal polymorphisms that affect drug metabolism. As a consequence, either the dose can be modified, or a different drug given.
2. (D1) A 45-year-old woman who missed a menstrual period has a positive pregnancy test. A 16 weeks gestation a fetal ultrasound examination is performed and nuchal thickening is noted. Which of the following tests on amniotic fluid is most appropriate to perform in this case?
A. Acetylcholinesterase
B. Alpha-fetoprotein
C. Human chorionic gonadotropin
D. Karyotyping
E. Polymerase chain reaction
F. Unconjugated estriol
Answer: D: Karyotyping.
The advanced maternal age and the nuchal thickening are strong indicators for possible fetal trisomy 21, which is diagnosed with the karyotype.
3. (D2) A 44-year-old man is worried about colon cancer because his sister was diagnosed with colon carcinoma at age 46. His aunt died from endometrial carcinoma at age 40. He is offered genetic testing. Which of the following is the greatest risk to him with performance and reporting of these tests?
A. Inability to obtain insurance
B. Increased risk for colon cancer
C. Radiation-induced carcinoma
D. Separation from his spouse
Answer: A: Inability to obtain insurance.
Genetic discrimination may occur when such testing reveals findings that increase the risk for subsequent disease, including cancer. Persons with such genetic risks may be treated differently by insurance companies or by employers.
4. (D3) A 48 year-old woman presents with breast tenderness and nipple discharge for the past 2 months. An ultrasound examination reveals cystic degeneration and the presence of focal calcifications in her right breast. A fine needle aspirate is performed in the mammography suite, and subsequent testing reveals the presence of HER2 gene amplification. Which of the following methodologies was most likely utilized to obtain this result?
A. ELISA
B. FISH
C. PCR
D. Southern Blot
E. Western Blot
Answer: B: FISH.
Gene amplification can be demonstrated by fluorescence in-situ amplification (FISH). The HER2 gene is amplified is some forms of breast cancer.
5. (D3) A quality assurance project in the laboratory reveals that over 90% of specimens submitted for polymerase chain reaction (PCR) testing for an uncommon organism were reported as positive in the past month. Which of the following is the most likely reason for this observation?
A. Increased prevalence of gene mutations in the organism
B. Mislabeling of specimens submitted
C. Reporting errors in the laboratory information system
D. Specimen cross contamination
E. Technical errors in test performance
Answer: D: Specimen cross contamination.
PCR and other molecular methods that detect minute amounts of genetic material are subject to errors from contamination in collection and performance of the test. These represent false positives that could be preanalytical or analytical errors.
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