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How Can I Avoid Getting A False Negative COVID-19 Test Result?

an employee is taking a swab test for covid-19
Mufid Majnun

The Ideastream Health Team is working to answer listeners’ questions about COVID-19, with help from local experts. You can send us your questions with our online form, through our social media group, or call us at 216-916-6476. We'll keep the answers coming on our website and on the air.

Rowan in Shaker Heights recently tested positive for COVID-19 after receiving a negative test result a few days earlier. He asked, “How can testing best be used to avoid false negatives? Does being vaccinated make you more likely to get a false negative from either kind of test?”

There are several potential reasons for false-negative test results, said Dr. Christine Schmotzer, vice chair of system pathology at University Hospitals.

One of the biggest is timing, she said. A person may test negative if there is not enough virus present in the sample, which can happen in the early days after contracting the virus, she said.

Once a person is feeling symptoms, they are recommended to get tested, Schmotzer said.

“Even if you have symptoms and you have a negative test, maybe there just wasn’t enough virus there at the time,” Schmotzer said. “We do advise that if people have a negative test and symptoms, that again, they talk to their doctor … and they may have them retest in another 1 to 2 days.” 

Another factor in the accuracy of a COVID-19 test is the type of test, she said. PCR tests – which are conducted and analyzed through a hospital or lab – are more accurate than rapid at-home antigen tests, like the kind people purchase in drug stores, she said.

“PCR will become positive with lower amounts of virus present,” Schmotzer said. “The PCR testing will have a lower [risk of] false negative than the rapid antigen testing.”

Rapid tests are still helpful in showing whether someone has COVID-19 at a given time, and they are most accurate when the person is symptomatic, she added.

Another common reason for a false negative is individual error, Schmotzer said. A person may have not gotten a good enough sample on the nasal swab - so she recommends reading the directions of at-home rapid tests carefully, she said.

“You have to do a really good quality swab,” Schmotzer said. “The swab needs to be far up enough in your nose as to be uncomfortable.”

When it comes to COVID-19 testing, the guidance depends on the situation, she added. If an individual is showing COVID-19 symptoms, they are typically advised to test as soon as possible, she said.

If the person came into close contact with someone who tested positive for COVID-19, the testing recommendations vary depending on whether they are vaccinated, she added.

If the individual is unvaccinated, they are recommended to get a COVID-19 test right away, but if they are fully vaccinated, they can take a test within 5 to 7 days after exposure for peace of mind, she added.  

The listener also asked if being vaccinated makes people more likely to get a false negative. There is a slight chance of this occurring, Schmotzer said, because research shows they do not shed as much of the virus as those who are unvaccinated. 

Copyright 2021 WCPN. To see more, visit WCPN.

Anna joined ideastream in 2019, where she reports on health news for WCPN and WVIZ in Cleveland. She has also served as an associate producer for NewsDepth. Before that, Anna was a 2019 Carnegie-Knight News21 fellow at Arizona State University's Walter Cronkite School of Journalism.