How Long to Wait After Covid Exposure to Get Tested
COVID-19 testing in the U.S. is more accessible and faster than it was at the beginning of the pandemic, but there's still much to consider when seeking it out.
Here's what to know about getting a coronavirus test right now. (This article does not address antibody tests; learn more about antibody testing.)
COVID-19 testing: What to expect
Most tests rely on a sample gathered one of four ways: nostril, saliva, back of the throat or deep inside the nose, aka nasopharyngeal, Dr. Eric Cioe-Pena, an emergency medicine physician at Northwell Health in New York City, told TODAY.
Looking at the mechanics of the test itself, there are two kinds. The most common is the polymerase chain reaction (PCR) test. Depending on the facility, these are usually sent to a lab off-site.
"(A PCR test) detects viral genetic code that does not exist in the human body otherwise," Cioe-Pena explained. "They're sensitive to the point where it will even detect fragments," which can mean that someone who was sick but then recovered could still test positive, he said.
The other kind is the antigen test, which can be done on-site and provide a rapid result within an hour or less, per the FDA. The first one was authorized in mid-May. They usually rely on a nasal swab and detect the coronavirus by looking for virus proteins in the body rather than genetic material.
The FDA has also authorized a few at-home tests. Most, if not all, use PCR technology and require a nasal or saliva sample. To get one, you may need approval from a health care provider.
When are they used and why?
The resources of the facility where you're being tested typically determine which type of test you'll receive and what type of sample is collected. At some places, you have the choice between an antigen and PCR test, but it's unusual to be able to choose what type of sample is taken. If you do have an option, though, know that nasopharyngeal is the "gold standard," per Cioe-Pena.
The default is usually a PCR test, but antigen can be a good option if having the result in an hour or less will determine what you or your doctor do next, explained Dr. James Finigan, a pulmonologist at National Jewish Health in Denver.
"If you're symptomatic and you're going to get a test and go home because you don't feel well ... there's really not a need for you to know that you have COVID-19 today versus tomorrow morning," Finigan told TODAY.
On the other hand, if you're a patient in a hospital and a doctor wants to admit you to a COVID-19 ward, or if you're a college student deciding whether you can safely return to your dorm, getting the results quickly matters.
Why does the timing for results vary so much?
Antigen tests are usually much faster than PCR tests because the facilities that offer them can process the test on site. Some facilities, like large hospital systems and local health departments, can also process PCR tests on site, which can lead to results within just a few hours.
But at facilities that must send PCR COVID-19 tests to a lab for processing, timing of results varies. Turnaround time tends to ebb and flow with testing demand, Cioe-Pena said. any labs processing results do so for an entire region. So, the timing of results may be "affected not only by your state but neighboring states," Cioe-Pena explained.
The "type of patient" can also affect turnaround time, he added. For example, at his hospital, "(intensive care unit) patients will get their tests faster than walk-ins."
Which are the most and least effective tests?
Cioe-Pena and Finigan both said the nasopharyngeal swab leads to the most accurate result. But some research shows the other swab types — throat, nostril and saliva — can be as sensitive, and Finigan said they're usually good enough to detect a "rip-roaring infection."
"If somebody has enough virus to really be able to spread it to somebody else, chances are you're going to get it in one of those tests," he added.
When looking at PCR versus rapid antigen tests, PCR tests are more accurate, especially if the result is negative.
"If you want to know whether you're positive, a rapid antigen test that's positive is a very strongly suggestive sign that you actually have COVID," Cioe-Pena said. "The false negative rate has been reported up to 50%, which is essentially a coin toss."
In fact, many places that offer rapid antigen testing will make patients sign a statement if they choose not to get a PCR test to back up the result of the antigen, he added.
Who should get tested for COVID-19?
The Centers for Disease Control and Prevention lists three different scenarios in which you should consider getting tested, but call your health care provider first.
- If you have COVID-19 symptoms (consider a drive-thru or at-home test to minimize exposing others, per Cioe-Pena)
- If you have close contact (within 6 feet for 15 minutes or more in one day) with someone with confirmed COVID-19
- If your health care provider or local health department recommends you get tested
Cioe-Pena also encouraged testing for people with secondary exposure, for example if someone in your household is a confirmed close contact of someone with COVID-19. He also believes there's value in routinely testing essential workers who regularly come in contact with lots of people, people living in hot spots, and in-person schools and offices. Many hospitals also test health care workers regularly.
Do not use testing as a way to justify high-risk behaviors, like large, indoor gatherings, or to prematurely end a quarantine that you've been ordered or advised to do.
"(A test) is still only a snapshot in a moment in time, and you really want the full spectrum of the 14 days with no symptoms," Cioe-Pena said.
Dr. Sten Vermund, dean of Yale's School of Public Health in New Haven, Connecticut, told TODAY that we should all be "making every effort to minimize (our) risk" and therefore need for a test with practices like social distancing, masking and hand-washing.
"Our testing is not limitless," he said. "We don't want people who don't have a good reason to get a test."
If you're not experiencing symptoms, the CDC suggests you consult your state's guidelines on current testing protocol.
When should I get tested for COVID-19?
If you have COVID-19 symptoms, the earlier you get a test, the better, Cioe-Pena said. "Based on the best data we've got, your viral shedding is very high one or two days before symptoms and for a period of several days during the first part of your symptoms."
If you think you've been exposed but don't have any symptoms, Cioe-Pena recommended waiting between five days and a week after exposure. "(Around) 70% of people are going to be symptomatic and or positive in five days," he explained.
Traveling? Some international destinations require visitors have a negative test before arrival. Follow the protocol and get tested within the appropriate timeframe.
Where to get a COVID-19 test:
Your state or local health department's website will likely have a list of facilities in your area that provide COVID-19 testing. Below are other options, but be sure to call in advance to check availability.
Coronavirus testing locations:
- Your primary care provider
- At your state or local department of health
- Urgent care centers
- Hospitals and emergency rooms
- Certain pharmacies, like Walgreens, CVS and Kroger
- At home, through an at-home testing service
Should you get tested for COVID-19 before visiting family?
Keep in mind that the best way to prevent spread of the virus is social distancing, Finigan said.
"Testing will give you a sense of, at that immediate point, you don't have detectable virus," he explained. "That doesn't mean you won't have detectable virus tomorrow. Is it better than nothing? Probably, but does it give you a license to go do what you want to do? I would say no."
Finigan said a 14-day quarantine before and after a visit would be the safest way to spend time with family (without mitigation measures in place). This means coming into contact with no one outside your household — no visits to grocery store or even walks outside, if you live somewhere populous.
Cioe-Pena suggested getting tested at the end of both quarantines, before seeing family and re-entering society.
This story was updated on Nov. 5, 2020 to include more up-to-date information on testing.
How Long to Wait After Covid Exposure to Get Tested
Source: https://www.today.com/health/covid-19-testing-what-can-you-expect-test-now-t186643