“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[1].

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.