One of the few consistent aspects of the coronavirus outbreak since it began in March has been confusion over testing, from where to get a test to their overall accuracy. Now, with much of the country seeing skyrocketing cases of COVID-19, the problem of limited access is even more salient.
In an effort to make testing more available, the Food and Drug Administration has authorized several types of tests that diagnose whether the patient has COVID-19 in that moment. Some can provide a reading within an hour; others you can take in your own home. Most, however, are still administered by a medical professional and require several days for results.
Here's a break down of the commonly used tests that detect a current coronavirus infection and how to make the most of your testing experience. (This article does not address antibody tests; learn more about antibody testing here.)
What are the different coronavirus tests available now?
Most tests rely on a sample gathered one of four ways: nostril, saliva, back of the throat or deep inside the nose, Dr. Eric Cioe-Pena, an emergency medicine physician at Northwell Health in New York City, told TODAY. He added that most facilities will only take a sample from one part of the body, and one person usually gets one test at a time.
Looking at the mechanics of the test itself, there are now two kinds. The most common, representing at least 90% of all COVID-19 tests, per Cioe-Pena's estimate, 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, per the FDA. The first one was authorized in mid-May. They usually rely on a nasal or throat swab and detect the coronavirus by looking for virus proteins in the body rather than genetic material. Because they're newer and the necessary tools are in short supply, these tests are not widely available, Cioe-Pena said.
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 typically need approval from your health care provider.
When are they used and why?
As states struggle to meet the demand for tests amid recent surges, the type of tests available and the resources of the facility where you're tested typically determine which one you'll receive. Therefore, it's unlikely you'll be able to choose the one you want.
"Usually the facility determines what the best test is for their institution," Cioe-Pena said.
For example, medical professionals must be trained on how to collect the best possible sample, so priority is usually given to one or two types. And the lab analyzing the samples may only have the ability to run certain types of tests.
For now, PCR tests are much more available, and rapid tests are "not the mainstay," Dr. Jake Deutsch, clinical director and co-founder of Cure Urgent Care in New York City, which has run more than 5,000 COVID-19 tests, told TODAY.
Cioe-Pena said his facility reserves rapid tests for when providers "need to make a medical decision very quickly." Say you had a heart attack and need to be admitted to a part of the hospital that does not house COVID-19 patients; then you need to test negative — and fast — to enter.
Deutsch added, "Different standards of care exist in different environments."
Why does the time it takes to get results vary so much?
The length of time to get a test result, again, depends on where you're tested. On average, it takes three to five days, Adm. Brett Giroir, the White House's director of testing, said on TODAY Tuesday.
Some places offer "point-of-care" tests (usually antigen based), meaning the testing center can process it on the spot, and those results take minutes. For tests that need to be sent to a lab, results can take anywhere from a day to two weeks, TODAY previously reported.
"It's not ideal when the virus incubation is two weeks, and the illness generally lasts at most for two weeks," Deutsch said.
The recent, increased demand for testing can slow things down, as well as the location of the lab itself. Some process results for an entire region of states.
"It's 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?
Deutsch and Cioe-Pena both said the deep nasal, aka nasopharyngeal, swab is the most accurate. Cioe-Pena added that his hospital has "made a conscious effort" to prioritize it.
"If a test is negative, we want to have as little doubt as possible that the patient is negative," Cioe-Pena said. "There's not a lot of convincing data the other swab types are as good."
Deutsch ranked the accuracy of the four sample types as follows, from most to least accurate:
When looking at PCR versus rapid, antigen tests, Cioe-Pena said PCR is more accurate in part because it can detect the virus in someone's system over a greater length of time. But PCR tests can also generate false positives for this reason. The FDA recently issued a letter warning that one of its authorized tests had a 3% false positive rate.
Still, Cioe-Pena said this is preferable to false negatives, which he believes are more likely with antigen tests. He added that he wouldn't use any of the antigen tests that he's familiar with "in isolation."
Cioe-Pena estimated that under ideal conditions, PCR tests are 99% accurate. Meanwhile, Deutsch said that rapid, antigen tests are about 93% accurate.
Cioe-Pena and Deutsch both expressed reservations about the accuracy of at-home tests because the quality of the sample depends on how well it's collected, and it's hard to take a deep nasal swab yourself. One pro, however, is they reduce crowding at testing centers.
How to get the best coronavirus test for your situation
To start, determine how important the accuracy of the test is to you. For example, if you're wondering if you can safely spend time with a high-risk individual, then it's crucial.
Next, locate testing facilities in your area and learn whether they require symptoms or approval from a health care provider.
Third, if you want a nasopharyngeal swab, research what it should feel like so you can tell if the sample was taken well, Deutsch said.
Last, call ahead and find out:
- What sample(s) does the facility take?
- Do they offer PCR or rapid, antigen tests?
- Who will take the sample, and how much experience do they have?
- How long is the turnaround time for getting a result, and where is the test sent? Especially important if you're in a time crunch.
- How will they communicate the results?
If you want a rapid test, which tends to be less accurate, Deutsch advised finding out whether your insurance covers it, as many do not and they can be expensive.
Cioe-Pena also suggested not seeking out a rapid test unless you "absolutely" need one.
Because we should still be staying home whenever possible at this stage in the outbreak, "my big question is where are you going that you need that test in an hour?" he said.