To help limit the spread of Covid-19 there are a number of tests available for those who are exhibiting symptoms or have come in contact with someone who has tested positive.
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Since the beginning of the Covid-19 pandemic, we've slowly come to learn about the variety of testing options given by health care facilities—many based on mucus and others that use saliva or blood. Given all of the options, how do you know which test is right for you? Do they all work the same way? Will tell you the same information? We will start with the basics.
There are currently two primary types of Covid-19 tests: diagnostic tests that look for active coronavirus infection in your mucus or saliva, and blood tests that hunt for antibodies—evidence that your immune system has encountered the infection before.
What Test Is Right For You?
The correct test depends on the reason for getting tested, such as confirming an active Covid infection; identifying asymptomatic or pre-symptomatic individuals who might be spreading the virus, or determining whether someone previously had Covid.
Here's what you should know about the different types of Covid tests, how they're used, and what they can tell you.
Molecular test (RNA or PCR test)
These diagnostic tests are considered the most sensitive when testing for active infection, and the results are highly accurate. You might take one if you or your doctor think you have Covid. You might also be asked to take this type of test if you need to prove to your employer or your college that you are not currently infected prior to returning to work or campus.
In most cases, a health care provider will collect mucus from your nose or throat using a specialized swab. Some molecular tests now use saliva, which can be less uncomfortable. Molecular tests are often called RT-PCR and PCR tests, short for polymerase chain reaction. Turnaround time varies from minutes to days or longer, depending on whether the sample is analyzed onsite or sent to an outside lab.
Tests using a nasopharyngeal swab—the one that goes deep into your nose to the back of your throat—are still considered the gold standard. But in recent months, at-home test kits have become available that allow people to collect their own sample (mucus or spit) and overnight it to a lab for analysis.
Antigen test (Rapid test)
This type of diagnostic test is often called a "rapid test" because the turnaround time is much quicker than a molecular test. It's also cheaper to produce. As a result, antigen tests are being used to screen large numbers of people, like at airports.
From a patient's point of view, antigen testing works in much the same way as molecular testing. Your health care provider will swab the back of your nose or throat to collect a sample for testing. But instead of waiting days for your results, an antigen test can produce a result in an hour or less. Antigen tests are highly accurate but these tests are more likely to miss active infection. If you have Covid symptoms but test negative, your doctor may order a molecular test just to rule out a false negative.
Antibody test (Serology test or blood test)
This test looks for antibodies from the coronavirus. Antibodies are proteins your immune system produces to fight off a foreign invader, such as a virus. A COVID-19 antibody test cannot diagnose active coronavirus infection. All it tells you is whether you've been infected at some point in the past, even if that occurred months ago. Antibodies do not become detectable until at least several days after an infection has started.
There are no FDA-approved, at-home antibody tests. You'll have to see a health care professional, who will take a blood sample via a finger prick or a blood draw from a vein in your arm. The vast majority of these tests are performed at a lab, which can take a couple of days to process. The first antibody tests have become available, making it possible for doctor's offices, hospitals, urgent care centers, and emergency rooms to get an answer within 15 minutes using blood from a person's fingertip.
Antibody testing isn't recommended until at least 14 days after the start of symptoms. If you test too early it may not provide an accurate result. Sometimes antibody testing is done along with viral testing when someone seeks care late in the course of their illness.