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How RT-PCR Works For COVID-19 Testing

How RT-PCR Works For COVID-19 Testing

There’s a lot of COVID-19 testing available right now but only RT-qPCR is recognized as the “gold standard” that many organizations accept.

With a rate of 99.5% accuracy for detecting COVID-19 samples, RT-qPCR is commonly used for COVID-19 testing for schools, workplaces, and even for travel.

That’s why in this guide we are going to go over RT-qPCR so you can have a better understanding of the process of why it’s highly recognized for determining whether or not you have COVID-19.


What is RT-qPCR?

RT-qPCR stands for Quantitative Reverse Transcription PCR which is just another way to say you are extracting a sample to detect if there is a virus. 

What we need to do is find the RNA with the help of an enzyme so that we can detect if there’s any genetic material of the virus.

This is important because if you can detect the genetic material, that means you can detect COVID-19 before you have any symptoms to take preventative action. In other words, what we are trying to do is detect if there’s any genetic material of the COVID-19 virus with RT-qPCR testing.

Extracting The RNA From The Sample

The first thing that you want to do is extract the RNA from the sample. Usually, the samples are from the extraction kits given to you which would include the cotton swab to the nose where it gets transported to the lab to get tested. What the lab technicians then do is they mix your sample into a solution called master mix which is made up of primers and probes.

Primers are the building blocks to build the RNA template while the probes are used to detect if there’s a COVID-19 virus.

Imagine primers as the building blocks to a ladder and you are trying to build the other half of a ladder. What the primers do is that they piece themselves together towards the ladder to create a full ladder. This is exactly what happens with your RNA template where the primers piece themselves correctly so that they can complete the entire RNA template. Now think of the probes as the security guards at the airport. If someone brings a metal watch to the metal detector, it’s going to go off and the security guard is going to know that they have some sort of metal on them. It’s the same with detecting the virus in the sample. 

If the probe detects any COVID-19 sample, it duplicates that piece and lights up letting you know that COVID-19 is there.


2. Duplicating The RNA Through The PCR Process

Now we go through the PCR process which is used to detect the genetic material of COVID-19.

The purpose of this is so that we can duplicate the samples so that it’s easier to detect the virus.

For example, imagine you’re staring down from a very tall building and you are trying to find one person wearing a red shirt. It’s going to be hard if just one person was wearing a red shirt. But imagine if over time people started changing their shirts to red because of a special event. It’s going to be a lot easier to spot one person wearing a red shirt if multiple people are wearing red shirts. Now imagine if there’s a billion people with red shirts in that crowd you’re watching and I guarantee that you would be able to spot one person wearing a red shirt.

That’s why RT-qPCR is very accurate in detecting COVID-19 samples because it duplicates billions of copies and it only needs to detect one sample to see if you have COVID-19.

3. Real Time or Quantitative Process

Now it’s time to determine if COVID-19 was detected in the sample. The way we detect if there’s a COVID-19 sample is by the amount of fluorescence given off from the sample. If there’s a sample with COVID-19, it’s going to emit light because of the probes. Now what happens is that it duplicates that sample with light making the entire sample emit more light making it easier to detect if there’s COVID-19. On the other hand, if there’s no light then that means that a COVID-19 sample was not detected and you’re good to go. That’s why it shows a flat line in the graph because there’s no light signal from the sample.



That was the entire process for RT-qPCR for COVID-19 testing. Let us know if you have any questions below about the process or if you have any concerns.

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