What Is the Difference Between a PCR and a COVID-19 Antigen Test?
You or someone you know has almost certainly received at least one COVID-19 test at this point in the pandemic.
But do you know what kind of test you got and what their strengths and weaknesses are?
I’m a molecular biologist, and I’ve been working on a National Institutes of Health-funded program called RADx since April 2020, which is assisting innovators in developing rapid tests to detect when a person is infected with SARS-CoV-2, the virus that causes COVID-19.
SARS-CoV-2 infection is diagnosed using two types of tests: molecular tests, also known as PCR tests, and antigen tests.
Each one detects a different aspect of the virus, and the way they work affects the test’s speed and accuracy.
So, how do these tests differ?
In search of genetic evidence
Obtaining a sample from the patient is the first step in any type of test.
A nasal swab or a small amount of saliva can be used for this.
Amplification of genetic material is the next step in PCR tests, which allows even a small amount of coronavirus genes in the patient’s sample to be detected.
A polymerase chain reaction (PCR) is used to accomplish this.
The sample is taken and treated with an enzyme that converts RNA to double-stranded DNA. The DNA is then mixed with a solution containing a polymerase enzyme and heated, causing the DNA to separate into two single-stranded DNA pieces.
The temperature is lowered, and polymerase binds to the single-stranded DNA and copies it with the help of a small piece of guide DNA called a primer.
Only coronavirus DNA is amplified as a result of the primers.
From the original one piece of RNA, you’ve now made two copies of coronavirus DNA.
These heating and cooling cycles are repeated 30 to 40 times in a laboratory machine, doubling the DNA and producing a billion copies of the original piece.
The fluorescent dye in the amplified sequence is read by a machine.
The ability of PCR to detect even the smallest amount of coronavirus genetic material in a sample is due to its amplifying property.
As a result, it’s a very sensitive and accurate test.
It’s the gold standard for diagnosing SARS–CoV–2 because of its near-perfect accuracy.
PCR tests, on the other hand, have flaws.
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