SM SM Virology & Molecular Diagnostics 1 — Questions and Answers
Question 1: Which nucleic acid amplification test characteristic is most important when evaluating a new molecular diagnostic assay for clinical use?
- Turnaround time for results
- Analytical sensitivity expressed as limit of detection (LoD) (Correct answer)
- Cost per test compared to culture methods
- Instrument footprint for laboratory space planning
Correct answer: Analytical sensitivity expressed as limit of detection (LoD)
The limit of detection (LoD) determines the lowest pathogen concentration the assay can reliably detect, directly impacting clinical sensitivity and diagnostic accuracy.
Question 2: SARS-CoV-2 RT-PCR testing uses reverse transcription because the viral genome is:
- Double-stranded DNA that requires denaturation before amplification
- Single-stranded RNA that must be converted to cDNA before PCR amplification (Correct answer)
- Segmented negative-sense RNA requiring special primers
- Circular RNA requiring rolling circle amplification
Correct answer: Single-stranded RNA that must be converted to cDNA before PCR amplification
SARS-CoV-2 is a positive-sense single-stranded RNA virus; reverse transcriptase converts genomic RNA into complementary DNA (cDNA) for subsequent PCR amplification.
Question 3: Which viral replication strategy is used by HIV to integrate into the host genome?
- Lytic replication using host RNA polymerase directly
- Reverse transcription of RNA to DNA, followed by integration via integrase (Correct answer)
- Rolling circle replication producing progeny genome copies
- Direct genome injection without replication intermediate
Correct answer: Reverse transcription of RNA to DNA, followed by integration via integrase
HIV reverse transcriptase converts the RNA genome to double-stranded DNA, which integrase then incorporates into host chromosomal DNA, establishing a provirus.
Question 4: In a multiplex PCR respiratory panel, a specimen tests positive for both influenza A and rhinovirus. What is the most appropriate interpretation?
- Repeat testing as co-infections are not clinically possible
- Report both pathogens — co-infection is possible and clinically significant (Correct answer)
- Report only influenza A as the dominant pathogen
- Request culture confirmation before reporting either result
Correct answer: Report both pathogens — co-infection is possible and clinically significant
Multiplex PCR can detect simultaneous co-infections; reporting both results is appropriate as co-infections occur and affect clinical management decisions.
Question 5: Which hepatitis virus is transmitted exclusively via the fecal-oral route and does NOT cause chronic infection?
- Hepatitis B virus (HBV)
- Hepatitis A virus (HAV) (Correct answer)
- Hepatitis C virus (HCV)
- Hepatitis D virus (HDV)
Correct answer: Hepatitis A virus (HAV)
HAV is a non-enveloped positive-sense RNA virus transmitted fecal-orally that causes self-limiting acute hepatitis without progression to chronic disease.
Question 6: The Baltimore classification system groups viruses primarily based on:
- Capsid symmetry (icosahedral vs. helical)
- Genome type and strategy for mRNA production (Correct answer)
- Presence or absence of a lipid envelope
- Host range (animal, plant, or bacterial viruses)
Correct answer: Genome type and strategy for mRNA production
The Baltimore classification groups viruses into 7 classes based on their genome nucleic acid type and the pathway used to produce mRNA for protein synthesis.
SM SM Virology & Molecular Diagnostics 1
Which nucleic acid amplification test characteristic is most important when evaluating a new molecular diagnostic assay for clinical use?