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FDA warns of false positive results from COVID-19 ‘rapid’ tests

Updated: Dec. 4, 2020 at 5:32 PM EST
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CHARLESTON, S.C. (WCSC) - The Food and Drug Administration is warning that the antigen tests used to detect COVID-19 can produce false positive results.

The tests are often available as “rapid” tests, and they can produce results within about 15 minutes. However, some patients question their accuracy as the FDA monitors reports of false positives.

Henry Herring visited the Charleston area last month to attend his brother’s funeral and see his sick mother.

Herring said he received a rapid COVID test from Holy City Medical, and his results came back positive and forced him to cancel his plans. Herring then returned to Holy City Medical to confirm his results with a PCR test, which is much more sensitive and can detect the genetic material that is specific to the virus.

The PCR test came back negative, contradicting the positive results he received just two days before.

“Because their COVID test was incorrect, now I’ve been put into a bind. I can’t get this time back, you know. I can’t uncremate my bother and go to his services. I can’t go back and see my mother…she’s got maybe 6 months,” Herring said.

The FDA said false positives can happen for several reasons, including when the tests are used for screening large populations with a low prevalence of infection or when users do not follow the test’s instructions.

Frank Wells, the CEO of Holy City Medical said only two rapid tests out of the thousands done at the facility have been confirmed to be false positives.

“Less than one out of 100 might find that positive result that’s really negative, which is why the PCR is recommended by the CDC and DHEC for confirmation of anything, and it’s still required for international travel in most places as well,” Wells said. “There are differences in accuracy between the two. Knowing a result within an hour or two is fantastic and tremendously convenient, but it’s not the end all.”

Holy City Medical’s medical director, Dr. Blake Willis, said if you’re having symptoms, you should get tested.

“If you have a negative rapid test but continue to have symptoms and you’re concerned about work or being around an elderly family member, especially going into the holidays, it would be wise to follow up with a confirmatory negative PCR test,” Willis said.

Wells added that Holy City Medical is offering rapid tests for fast same-day results with no appointment or screening needed for $80. Testing is done through a drive-thru so patients can stay in their vehicles.

Meanwhile, the South Carolina Department of Health and Environmental Control said Friday, “DHEC does not track false negatives. We have noted that there are instances of antigen testing – which is not PCR testing – producing false positives or negatives. These are often available as “rapid” tests In some cases, a positive antigen test is recommended to be followed-up with a confirmatory PCR test. Please note that DHEC-sponsored testing locations only offer PCR testing, not antigen testing.”

These concerns about false positives come as DHEC prepares to distribute thousands of rapid tests to school districts across the state.

“DHEC anticipates that an initial allotment of Abbott BinaxNow test kits, which return results in 15 minutes, will reach districts next week in an amount equivalent to 10% of their student and staff populations. Since the plan is voluntary for districts, their plan of implementation and tracking at the school level can likely be found either by contacting the S.C. Department of Education or the districts directly,” DHEC officials said in a statement.

DHEC confirmed these rapid tests are the same brand received in South Carolina back in April and the same tests being used in select nursing homes, assisted living facilities and home health services, as well as several Historically Black Colleges and Universities.

However, DHEC officials said health care facilities and doctors’ offices may have purchased their own rapid-test devices.

“Every facility and office across the state that may offer rapid testing isn’t necessarily reported to or tracked by DHEC,” according to DHEC officials.

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