Between sample collection, transportation, amplification, detection and reporting, it can take from 12 hours to five days for a person to get results back. Usually only large, centralized testing facilities – like hospital labs – can conduct many PCR tests at a time. They require a skilled laboratory technician and special equipment to run them, and the amplification process can take an hour or more from start to finish. However, PCR tests have some weaknesses too. With accuracy that approaches 100%, it is the gold standard for diagnosing SARS–CoV–2. This makes it a highly sensitive and accurate test. The amplifying property of PCR allows the test to successfully detect even the smallest amount of coronavirus genetic material in a sample. The amplified sequence contains fluorescent dye that is read by a machine. Laboratory machines repeat these heating and cooling cycles 30 to 40 times, doubling the DNA until there are a billion copies of the original piece. You’ve now created two copies of coronavirus DNA from the original one piece of RNA. The primers ensure that only coronavirus DNA is amplified. The temperature is lowered, and polymerase, with the help of a small piece of guide DNA called a primer, binds to the single-stranded DNA and copies it. Then, the DNA is mixed with a solution containing an enzyme called a polymerase and heated, causing the DNA to separate into two single-stranded DNA pieces. A healthcare worker takes the sample and treats it with an enzyme that converts RNA into double-stranded DNA. This is done using a technique called a polymerase chain reaction. This can be a nasal swab or a bit of saliva.įor PCR tests, the next step is amplification of genetic material so that even a small amount of coronavirus genes in the patient’s sample can be detected. The first step for either kind of test is to get a sample from the patient. So what are the differences between these types of tests? Looking for genetic evidence Each detects a different part of the virus, and how it works influences the test’s speed and relative accuracy. Two major types of tests are used to diagnose infection with SARS-CoV-2: molecular tests – better known as PCR tests-and antigen tests.
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