21/08/2022
Why qPCR is the gold standard for COVID-19 testing
Every day there’s a new headline about the best ways to test for SARS-CoV-2 virus, the virus that causes COVID-19. In the following Q&A, Joshua Trotta, Senior Director Business Development, at ThermoFisher discusses what you need to know about qPCR, the gold standard for COVID-19 testing. This is a follow-up to our “How does a COVID-19 test work?” interview with Joshua on Science with a Twist earlier this year.
What is an RT-qPCR test?
“PCR” is shorthand for “polymerase chain reaction,” a scientific methodology to make millions and billions of copies of a specific DNA sample, which for the past 25 years has been one of the most widely used techniques in molecular biology.
The genetic material in SARS-CoV-2 virus is stored in RNA. In the case of COVID-19 testing, RNA from a SARS-CoV-2 sample is first converted to its complementary DNA sequence by a process called reverse transcription (RT). The DNA thus transcribed is amplified by qPCR, where “q” stands for “quantitative”; hence the technique is called RT-qPCR.
RT-qPCR can detect the genetic information (RNA) of the novel coronavirus—even if the virus is present in extremely small amounts. Researchers estimate that RT-qPCR can detect as little as ~1,000 copies of viral RNA per milliliter, or 10 copies per analytical limit of detection (LoD). This means it is possible to diagnose someone as positive for COVID-19 even when their sample contains a very small amount of virus.
This means that COVID-19 RT-qPCR tests are not only able to detect the virus’s genetic information, they are also able to quantify the amount of that genetic information that is present in a sample. The Applied Biosystems TaqPath COVID-19 Combo Kit from Thermo Fisher Scientific is designed to detect the presence of the virus at very low levels and uses an algorithm to provide a positive or negative result.
How is a SARS-CoV-2 sample collected for RT-qPCR testing?
Samples can be collected in a
