4 Questions You May Have About COVID-19 Testing, AnsweredJuly 14, 2020 - Katie McCallum
These days, just one cough or two is all it takes to question whether or not you might have COVID-19.
Knowing whether or not you're infected with coronavirus can help protect not only your own health, but the health of our entire community — so it's important to get tested if you think you have COVID-19.
COVID-19 testing can feel like a mysterious process, but Dr. Wesley Long, director of diagnostic microbiology at Houston Methodist, is here to answer common questions you may have about when, where and how to get tested.
Who should get tested for COVID-19?
The most important time to get tested is if you're experiencing symptoms, including:
- Dry cough
- Shortness of breath
- Sore throat
"It's also important to get tested if you've been in close contact with someone who has tested positive, even if you don't have symptoms yourself and even if you're vaccinated," says Dr. Long. "Since it can take anywhere from two to 14 days to develop symptoms, and some people never develop symptoms or have symptoms that are very mild, getting tested can help prevent you from inadvertently spreading the virus if you're sick and don't know it."
Where can I get tested for COVID-19?
"There's a lot of confusion about what a person needs to do in order to get tested for COVID-19," says Dr. Long. "And, in reality, these steps vary based on where you get tested."
Getting tested at a Houston Health Department-affiliated site is free, fast and safe.
In addition, Houston Methodist offers COVID-19 testing to patients. You'll need an order from your doctor as well as a scheduled appointment. If you're worried you have COVID-19, talk to your doctor about scheduling a test and call 713.441.5509 for directions to the appropriate location.
"There are also many urgent care centers and other quick clinics that are offering COVID-19 testing, which may or may not require pre-screening," says Dr. Long.
In addition, you can be screened for COVID-19 virtually by one of our board-certified care providers through Houston Methodist Virtual Urgent Care. Our providers are available 24/7 to help determine if you need testing, as well as advise you where to go.
What's the difference between the COVID-19 tests available?
There are three types of tests available for COVID-19:
- Polymerase chain reaction (PCR) testing
- Antigen testing
- Antibody (serology) testing
"Each of the COVID-19 tests works a little bit differently, and determining which test you need depends on: what's most accessible for you, whether it's being used as a diagnostic tool and whether you're planning to donate plasma after your recovery," explains Dr. Long.
Different testing sites will likely have different COVID-19 testing options. Before choosing a testing site, make sure it offers the test you're looking for.
PCR test for COVID-19
To diagnose COVID-19, the current gold standard is a PCR test.
"A PCR test can help determine whether or not you're currently infected, and the results are fairly reliable — meaning few false positives and few false negatives," says Dr. Long. "A false positive is when you test positive but you're not actually sick. A false negative is when you test negative but you are actually sick."
During a PCR test for COVID-19, a nasopharyngeal swab is taken by a health care provider. This swab is then processed by a lab, and it can take anywhere from 24 hours to several days to receive your results.
A positive PCR test result means you either currently have COVID-19 or have very recently have had COVID-19.
A negative PCR result means that you likely weren't infected at the time of testing, but it doesn't mean you can't get COVID-19 in the future.
Antigen test for COVID-19
An antigen test is another diagnostic test for COVID-19, helping to determine if you're currently infected with coronavirus.
"This type of test is faster and requires fewer resources than a PCR test, but antigen tests are also less sensitive," explains Dr. Long. "In particular, antigen tests come with a higher chance of false negatives than PCR tests — meaning your test may come back negative even if you are infected with COVID-19."
During an antigen test for COVID-19, a nasal or throat swab is taken by a health care provider. Sometimes the swab can be tested at the point of care while you wait, but in other cases the swab may need to be sent to a lab for processing and testing.
A positive antigen test result means you have COVID-19.
A negative antigen test result means you may not currently be infected, but if your symptoms persist a PCR test can help confirm your results.
"While a positive antigen test is a reliable confirmation of a COVID-19 case, a negative antigen test does not mean you're not infected," warns Dr. Long "Given the higher rate of false negatives with antigen tests, a PCR test is needed to confirm a negative antigen test result."
Antibody test for COVID-19
"An antibody test can help determine if you've had COVID-19 recently, but it shouldn't be solely used to diagnose a current infection," says Dr. Long. "For the most part, antibody tests are primarily being used to help determine which recovered COVID-19 patients qualify to donate convalescent plasma to help treat critically ill COVID-19 patients."
A positive antibody test result may indicate a recent infection, but antibodies typically don't become detectable until 4 to 5 days after symptom onset at the earliest. In addition, a positive result doesn't mean you were definitely infected in the past.
"With an antibody test, false positives are possible," explains Dr. Long. "This means that a person who hasn't had COVID-19 may test positive with this test."
A negative antibody test result may mean you haven't been infected with coronavirus in the past, but not always.
"A negative antibody test result doesn't necessarily mean you haven't had COVID-19. There's a lot we still don't know about the immune system's antibody response to coronavirus, including how long these antibodies persist and provide protective immunity in a previously infected person," explains Dr. Long.
What happens after a positive COVID-19 test result
If you test positive for COVID-19, you'll need to self-quarantine. During this time, stay inside your home, ideally in a separate room from other people in your household.
"In fact, if you're showing symptoms or have come into close contact with someone who has COVID-19, you'll want to start self-quarantining in between the time you get tested and get your results," suggests Dr. Long. "You'll want to be sure you're not inadvertently spreading the virus in the meantime in case you do actually have it."
Most people with COVID-19 experience mild symptoms that can be treated at home through pain relievers, cough medications, rest and hydration.
"If you have questions or concerns about your symptoms or need follow-up care, start by calling your doctor," says Dr. Long. "If your symptoms are severe, such as high fever and/or shortness of breath, you should go to your nearest emergency room."