Difference Between PCR and Antigen COVID-19 Tests?

At this point in the pandemic,chances are you or someone you know has been tested for COVID-19 at least once.But do you know which test you took and the pros and cons of these different tests?Two main types of tests are used to diagnose SARS-CoV-2 infection: molecular tests (better known as PCR tests) and antigen tests.Each detects a different part of the virus and how it works affects the speed and relative accuracy of the test.So what is the difference between these types of tests?

Search for genetic evidence

The first step in any kind of test is to obtain a sample from the patient.This could be a nasal swab or a bit of saliva.For PCR testing,the next step is to amplify the genetic material so that even small amounts of coronavirus genes in patient samples can be detected.This is done using a technique called polymerase chain reaction.A healthcare worker removes the sample and treats it with an enzyme that converts the RNA into double-stranded DNA.The DNA is then mixed with a solution containing a polymerase and heated to separate the DNA into two single-stranded DNA fragments.The temperature is lowered,and the polymerase,with the help of a short piece of guide DNA called a primer,binds to the single-stranded DNA and copies it.Primers ensure that only coronavirus DNA is amplified.You have now created two copies of the coronavirus DNA from the original piece of RNA.The amplification properties of PCR allow the test to successfully detect even the smallest amount of coronavirus genetic material in a sample.This makes it a highly sensitive and accurate test.It is nearly 100% accurate and is the gold standard for diagnosing SARS-CoV-2.However,PCR testing also has some weaknesses.They require skilled lab technicians and special equipment to run them,and the amplification process can take an hour or more from start to finish.Often only large,centralized testing facilities such as hospital laboratories can perform multiple PCR tests at once.Between sample collection,shipping,amplification,testing,and reporting,it can take anywhere from 12 hours to five days for a person to get a result.Finally,they're not cheap,$100 or more per test. 

Antigen tests

Rapid,accurate testing is critical to contain highly contagious viruses like SARS-CoV-2.PCR tests are accurate but can take a long time to produce results. Antigen tests,the other major type of coronavirus test,are much faster but less accurate.Antigens are substances that cause the body to mount an immune response they trigger the production of antibodies.These tests use lab-made antibodies to look for antigens of the SARS-CoV-2 virus.To perform an antigen test,you first treat the sample with a liquid containing salt and soap to break up cells and other particles.This fluid is then applied to a test strip coated with a thin line of antibodies against SARS-CoV-2.Just like the antibodies in your body,the antibodies on the dipstick will bind to any antigens in the sample.If the antibody binds to the coronavirus antigen,a colored line will appear on the test strip,indicating the presence of SARS-CoV-2.

Antigen testing has many advantages.First,they are so easy to use that even people without special training can perform them and interpret the results even at home.They also provide quick results,usually in less than 15 minutes.Another benefit is that these tests are relatively inexpensive.Antigen tests do have some drawbacks.Depending on the circumstances,they may not be as accurate as PCR tests.Antigen tests are very accurate when a person has symptoms or has a lot of virus in their body.However,unlike molecular PCR tests,antigen tests do not amplify what they are looking for.That means there needs to be enough viral antigen in the sample for the antibodies on the strip to produce a signal.When a person is in the early stages of infection,there isn't much virus in the nose and throat,which is where samples are taken.Therefore,antigen testing may miss early cases of COVID-19.It is also at this stage that a person does not have any symptoms,so it is more likely that they will not know they are infected.

OTC Home Test Increases Consumer Access to Rapid Testing

Home Test,an over-the-counter (OTC) COVID-19 antigen test,adds to the growing list of tests that can be used at home without a prescription.This action underscores our continued commitment to increasing the availability of appropriately accurate and reliable OTC tests to meet public health needs and increase consumer access to testing.Today's mandated COVID-19 home testing should significantly increase the availability of rapid at-home testing and is expected to double rapid at-home testing capacity in the coming weeks.By the end of the year,manufacturers plan to conduct more than 100 million tests per month,a number that will rise to 200 million per month by February 2022.More than 400 COVID-19 testing and sample collection devices authorized since March 2020, including authorization of rapid OTC at-home tests,deems at-home COVID-19 diagnostic tests a high priority and continues to prioritize reviewing them Given their importance to public health.Most antigen tests for home use are mandated to perform serial testing,or to test the same person multiple times over several days.These authorizations follow the announcement of a simplified approach to help facilitate the authorization of rapid tests for use in conjunction with serial testing procedures,which increases access to testing for consumers.Notably,the COVID-19 Home Test does not require serial testing based on data provided for asymptomatic individuals.Today's authorization will facilitate greater access and testing capabilities.Remind patients that false negative and false positive results are possible with all tests.Individuals who test positive should self-isolate and seek additional care from their healthcare provider.Individuals who test negative and develop COVID-like symptoms should follow up with their healthcare provider,as negative results do not rule out COVID-19 infection.We believe home diagnostic tests play a critical role in the fight against COVID-19.We will continue to provide support and expertise to help develop appropriately accurate and reliable tests and promote greater access to testing for all.The Department of Health and Human Services protects public health by ensuring the safety,effectiveness,and security of human and veterinary drugs, vaccines and other biological products for human use,and medical devices.The agency is also responsible for the safety and security of our nation's food supply,cosmetics,dietary supplements,products that emit electronic radiation,and regulation of tobacco products.