Not all COVID-19 tests are the same. What type should you get?

Coronavirus

AUSTIN (KXAN) — As COVID-19 case counts continue to rise in Texas and as Austin COVID-19 testing sites continue to see an increase in people seeking tests, you might find yourself among the many people considering getting tested.

As access to testing has increased relative to earlier in the pandemic, there are a range of ways you can get tested and types of tests available. But COVID-19 tests can vary in how accurate they are and how quickly you can get results.

KXAN compiled information from state, local and national health agencies as well as insight from local public health experts to offer you a guide on your COVID-19 testing options.

The overview

A graphic comparing molecular, antigen, and antibody COVID-19 tests using information from the U.S. Food and Drug Administration, Austin Public Health, Texas Department of State Health Services. (KXAN Graphic Rachel Garza).

It is important to note COVID-19 testing does not guarantee your safety and does not eliminate the high risk of COVID-19 spread that comes with attending gatherings or indoor celebrations.

As Austin Public Health emphasized, “Getting a negative COVID-19 test is not a replacement for safely self-isolating.” The department said having a virtual holiday celebration or celebrating only with members of your own household is the best option this holiday season.

Comparing the types of tests

PCR testing is the type of COVID-19 test APH recommends and is referred to by the U.S. Food and Drug Administration as “highly accurate” and “usually does not need to be repeated.”

Ana Urueta, a public health and emergency preparedness planner for Austin Public Health advised, “the number one thing to do if you find out you’ve been exposed to a confirmed [COVID-19] case is to isolate yourself, prevent yourself from being around anybody.”

A staff member administers a nasal swab COVID-19 test at a drive up testing site run by Austin Public Health. Image Courtesy City of Austin.

Austin Public Health advises that you should get tested for COVID-19 if you have been exposed to someone else who is a confirmed positive case or if you are experiencing COVID-19-like symptoms. You can take a screening for the department to see if you need a COVID-19 test here.

She recommends waiting at least two to three days after your initial exposure to the virus before you take a COVID-19 test. Urueta said if you take a test immediately after you have been exposed, the virus will likely not show up on a test at that point.

“It is very important to complete the quarantine for the full 14 days because that is how long it could take for you to develop the virus. And also it’s very important to remember that you cannot test your way out of quarantine, because the virus could pop up at the very last minute and you could be contagious and not know it.”

Ana Urueta, Public Health Emergency Preparedness Planner for Austin Public Health

The FDA explains there are two types of coronavirus tests: diagnostic tests and antibody tests. There are also two types of diagnostic tests: molecular tests like PCR tests that detect the virus’ genetic material and antigen tests that detect specific proteins from the virus.

Molecular tests and antigen tests can diagnose you with active coronavirus infection. Antibody tests can show that you’ve been infected with coronavirus in the past.

The state’s standards for classifying cases also reflect the higher accuracy level molecular tests have. According to the standards used by the Texas Department of State Health Services, the only COVID-19 cases which are reported as “confirmed” are those which showed a positive result through a molecular test.

DSHS reports a positive result through an antigen coronavirus test as a “probable” case, meaning that it won’t be counted in the state’s total number of cases. A positive result on an antibody test will not be considered a “confirmed” or a “probable” case in the state’s numbers.

At the start of the pandemic, the state reported all of these numbers together, but on May 13, the state started reporting molecular and antibody tests separately. Then on August 6, the state began reporting antigen test totals separate from the molecular tests.

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People stand in line for a COVID-19 test in Austin. (Nexstar Photo)

APH said it’s important to note molecular tests and antigen tests are not the same things. APH only recommends antigen tests “in certain circumstances.” The department sometimes encourages antigen tests to get results quickly “and tamp down potential spread.”

“They are not recommended in the sense that they do not by themselves make someone ‘safe’ from COVID-19 if they get a negative test,” a spokesperson from APH explained.

Urueta said you can take an antigen test if you chose to, and if your results are positive your case will be considered a presumed positive, but if your results are negative Austin Public Health will recommend you follow up with a PCR test.

Molecular testing

Molecular testing includes PCR, RT-PCR, NAAT, and LAMP testing, the Texas Department of State Health Services (DSHS) says.

In most cases, this testing is performed through a nasal swab, a nasopharyngeal swab, a throat swab, or saliva. The FDA said in some locations, molecular test results can be returned within the same day the test was taken, but in other locations, it can take a week or longer to get results. KXAN’s reporting this week indicates that molecular COVID-19 test results have been taking between one to five days to be returned to patients depending on where they test.

An Austin Public Health drive-up COVID-19 site. (Photo Courtesy City of Austin).

All of Austin Public Health’s COVID-19 testing — whether done in-home or at testing sites– is done through PCR tests, Urueta explained. APH uses nasopharyngeal testing which sticks a swab very far up your nose because that gives them “a higher probability of getting a good collection sample.”

She said APH recommends and relies on PCR testing because it has a better chance of being able to detect the virus, “especially if you’re not experiencing a lot of symptoms and you don’t have a high viral load.”

Not only is this type of testing recommended by Austin Public Health, it is also the type of testing recommended by CommUnity Care, which provides healthcare services with a focus on those who are uninsured in Austin and Travis County.

A Baylor Scott & White drive through COVID-19 test site in Austin. (KXAN Photo/ Kaitlyn Karmout).

Baylor Scott & White Health, who bills itself as the largest not-for-profit health system in Texas said in a statement that throughout the areas they serve, they “primarily use real-time PCR-based in vitro diagnostic tests for the identification of SARS-CoV-2 virus — the virus that causes COVID-19.”

These tests are collected by BS&W through nasopharyngeal swabs.

A spokesperson for BS&W noted that they use the RT-PCR test because its shown to be the most accurate.

“As new testing options become available, we are watching with great interest as these go through validation and FDA review,” the statement from BS&W noted.

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Antigen testing

In most cases, this testing is performed with either a nasal swab or a throat swab. DSHS noted that antigen testing can be less expensive than a molecular test.

The FDA explained that antigen tests can be returned very quickly, with some taking as few as fifteen to thirty minutes on the result. But despite the quick turnaround time offered by antigen tests, the FDA noted antigen tests have a higher chance of missing an active infection than a molecular test.

Urueta with Austin Public Health said while antigen tests can be performed quickly, but also “has a high probability of potentially missing if the individual has COVID and it could give you a false negative because it might not detect it.”

Some spots in Travis County, like Tarrytown Pharmacy, are offering rapid antigen testing. (KXAN Photo/Chris Nelson)

If you test positive using an antigen test, Urueta said, then you likely do have COVID-19. However, the FDA notes that false positives with antigen tests do happen, especially in areas where many people do not have the virus.

CommUnity Care’s health center locations provide antigen testing to patients as a screening tool because the results from antigen tests can be returned immediately. If the results are negative, the patient will then be sent to take a PCR test to confirm that negative.

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Antibody testing

Also referred to as serology testing, antibody testing is done by using a finger stick or a blood draw. DSHS noted that a positive antibody test means that “the person being tested was infected with COVID-19 in the past and that their immune system developed antibodies to fight it off.”

Additionally, a person could be currently infected with COVID-19 and still test negative on an antibody test, DSHS added.

The FDA explained that antibody test results are available on the same day the test was taken in many locations, though some results may take one to three days.

MIAMI LAKES, FLORIDA – JULY 22: Dr. Jacqueline Delmont, Chief Medical Officer of SOMOS Community Care, takes blood from a person for a COVID-19 antibody test in a medical tent at a testing site locate at the Miami Lakes Youth Center on July 22, 2020 in Miami Lakes, Florida. Testing is being provided by doctors from New York City associated with SOMOS Community Care, as the state of Florida experiences a surge in coronavirus cases. (Photo by Joe Raedle/Getty Images)

Urueta explained that Austin Public Health does not perform or recommend antibody tests.

“Our objective is to try to identify if the person is currently experiencing an infection and the antibody test might tell you if the person has the antibodies present in their body — so perhaps they were sick several months ago — but it doesn’t necessarily tell you if the person is currently infectious,” she added.

State health leaders explained that antibody tests can be helpful in determining who qualifies to donate convalescent plasma and can be used to indicate the percentage of COVID-19 in a community if “lots of people in the community” take the test.

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What about rapid testing?

Rapid testing refers to the length of time it takes for test results to be returned, rather then the means of the test itself. Rapid tests can be antigen tests or PCR tests.

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Line for rapid COVID-19 testing outside Austin High School on Nov. 16, 2020 (KXAN photo/Ed Zavala)

Urueta said rapid PCR tests fall into the category of tests Austin Public Health recommends, though they are harder to come by than the PCR tests that take a day or more to return.

But she noted that a rapid antigen test should be followed by a PCR test because the antigen test might miss the virus.

The U.S. Department of Health and Human Services (HHS) announced Thursday that it has launched a pilot program with five states, including Texas, to use portable molecular COVID-19 tests that provide results in around 20 minutes. HHS said this was the same COVID-19 test used to control the spread of the virus in the National Basketball Association “bubble.”

Last week, the department said it distributed 4,500 test kits and 100 cartridge readers to Texas.

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