Question
Identify the incorrect statement in relation to the testing of COVID-19.
| A. | Most predominant method of diagnosis of Covid 19 is RT-PCR |
| B. |
First line screening assay: N gene assay |
| C. |
Confirmatory assay: RdRp gene assay |
| D. |
Peripheral ground glass opacities on CT is the hallmark feature |
|
Correct Answer » B Explanation |
 |
Option A: The most commonly used method for diagnosis of COVID-19 is RT-PCR
Correct.
RT-PCR is the standard laboratory method used for the diagnosis of active SARS-CoV-2 infection. It detects viral RNA and has been the most widely used diagnostic test throughout the pandemic.
Option B: First-line screening assay: N gene assay
Incorrect.
According to the WHO-recommended early RT-PCR protocols and the widely cited Corman et al. protocol:
- E gene (Envelope gene) assay is used as the first-line screening assay.
- Positive samples are subsequently confirmed using a more specific target.
Therefore, the statement that the N gene assay is the first-line screening assay is incorrect.
Option C: Confirmatory assay: RdRp gene assay
Correct.
The RNA-dependent RNA polymerase (RdRp) gene assay is highly specific for SARS-CoV-2 and has been used as a confirmatory assay following an initial positive screening test.
Typical testing strategy:
- Screening: E gene assay
- Confirmation: RdRp gene assay
Option D: Peripheral ground-glass opacities on CT is the hallmark feature
Correct.
The characteristic CT chest findings in COVID-19 include:
- Bilateral ground-glass opacities
- Peripheral distribution
- Posterior and lower lobe predominance
Although CT is not the primary diagnostic test, peripheral ground-glass opacities are considered the hallmark radiological feature of COVID-19 pneumonia.