ABOUT RT-PCR COVID TESTS.
RT-PCR COVID-19 Test
RT-PCR COVID-19 Testing is considered the “gold standard” in SARS-CoV-2 detection. This test actually detects RNA (or genetic material) that is specific to the coronavirus and can detect its presence within days of infection, even those who have no symptoms. This is what makes RT-PCR COVID testing the most reliable test to detect symptomatic and asymptomatic carriers of coronavirus.
The turnaround time to receive a COVID testing result is very quick, within 24 to 48 hours.
Once a sample is produced, it is sent to the lab where its contents are placed into a PCR machine which performs the actual test. To find the coronavirus you need to replicate its genetic material so there is more of it and it’s easier to detect.
In the case of coronavirus specifically, you cannot do this directly because it is what’s called an “RNA virus.” This means that the genetic material of the virus is RNA, not DNA. Other RNA viruses include the flu, measles, or rabies. RNA is fragile. It’s single-stranded, not double-stranded like DNA. It also has a different backbone structure which makes it degrade more easily. For instance, if hair or skin particles flake off onto it, it degrades. So if you try to replicate the RNA genetic material, it will likely break down, and you wouldn’t be able to identify the virus. To get around this, the first step in the process is to convert the RNA into DNA by introducing a tiny molecular machine that turns the single strand into a double strand. This tiny machine is an enzyme (a biological chemical) called reverse transcriptase. So (very technically) the PCR process that is used for coronavirus is an “RT-PCR” (reverse transcriptase PCR), since we start with RNA and then transform it into DNA.
Once the DNA is produced, the second step in the RT-PCR COVID testing process is to target the SARS-CoV-2 viral sequence for copying. Right now, your genetic material and the virus’s genetic material (if you’re infected) are all mixed together in one big soup. Scientists will select a short string of genetic material that is only in the coronavirus and not in human DNA. If they find these strings of genetic material, they copy this part of the viral DNA over and over again by a copy machine (an enzyme) that can only recognize this string of material. That small section of the coronavirus genetic material gets copied over and over again — literally millions of times — which makes the genetic material easier to detect. Ultimately if the coronavirus is present, the PCR machine will be able to detect the copies and produce a positive result. If there is no coronavirus genetic material, nothing will be copied, and the test result will be negative.
Rapid Test (Antigen)
Antigen tests generally look for proteins associated with the virus rather than the genetic material. Antigen tests are faster than the typical PCR tests but tend to miss more infections. It’s important to note that antigen tests have a higher rate of false negatives than PCR tests, so even if you get a negative antigen test result, you might still have the virus.
If you have recently tested negative on a rapid test but still have symptoms, our current recommendation is to have a confirmation test performed with an RT-PCR COVID test. This is especially true if you’ve had a high-risk exposure. A high-risk exposure is considered more than 15 minutes of contact with a COVID-positive individual in a 24-hour period and you have been within 6 feet of this individual.