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‘10-minute diagnostic tests not recommended due to inaccuracy’ 
  • By Song Soo-youn
  • Published 2020.03.19 15:49
  • Updated 2020.03.26 12:05
  • comments 0

As the world is grappling with the new coronavirus pandemic, many have called for the introduction of rapid diagnostic tests (RDTs), which can produce results in around 10 minutes.

Healthcare experts, however, did not recommend using them due to inaccuracy, at a YouTube show Tuesday by K-Healthlog, a channel operated by The Korea Doctors’ Weekly.

RDT results come out quickly, compared to real-time polymerase chain reaction (PCR) tests now used in Korea, which take about six hours to screen out COVID-19 patients. However, RDTs have 50 to 70 percent of sensitivity, compared to PCR tests, meaning that a COVID-19 patient could test false-negative, or a healthy person could test false-positive. Such inaccuracy will add confusion, experts said.

Diagnostic testing for viral infections includes molecular diagnosis, cell culture, and antigen/antibody testing. RDTs use antigens or antibodies. Usually, it takes about two to four weeks for a human body to develop an antibody against infectious disease, antigen detection is used more for RDTs than antibody detection.

Healthcare experts discuss testing COVID-19 during a YouTube show by K-Healthlog on Tuesday, a channel operated by The Korea Doctors’ Weekly. From left are Lee Hyuk-min, director of infection control affairs at the Korean Society for Laboratory Medicine, Kang Yang-gu, a science journalist, Shin Hyun-young, a professor of family medicine at Myongji Hospital, and Lee Wang-jun, chairman of Myongji Hospital.

Lee Hyuk-min, director of infection control affairs at the Korean Society for Laboratory Medicine, said it was too early to introduce RDTs during a YouTube live show, K-Healthlog, hosted by The Korean Doctors’ Weekly, on Tuesday.

“Antibody testing can check the viral infection by targeting an antibody that develops after a virus gets into a human body. But the entry of a virus does not create an antibody right away,” Lee said. “So, we use antibody testing in the late-stage viral infection to look at epidemiologic linkage rather than in the early-stage infection.”

Antigen testing, often used in RDTs, is also inaccurate, compared to molecular diagnostics, he noted.

“Antigen testing amplifies a signal using various methods. So, their sensitivity is lower than the PCR tests. In clinical settings, the sensitivity of antigen testing for influenza infection is 50-70 percent of that of PCR tests,” Lee explained.

Antigen testing requires several conditions, and the most important condition would be persuading the public to tolerate inaccuracy of the test, Lee went on to say.

“If a diagnosis of flu goes wrong, a patient might get angry, but it won’t be a serious problem. But if COVID-19 testing gets wrong, it will be more than that,” Lee said.

On the condition that a treatment is available and quick diagnosis is necessary, antigen testing could help, he said. However, the nation has to mitigate the spread of COVID-19 as much as possible, so physicians are doing PCR tests, not antigen testing, he added.

Shin Hyun-young, a professor of family medicine at Myongji Hospital, said flu offers many other options for physicians because doctors could still prescribe Tamiflu at their discretion despite a wrong diagnosis.

‘Korea capable of 20,000 daily PCR tests, no need for RDTs’

In a joint statement, six diagnostics societies in Korea said, “It is very dangerous to introduce rapid diagnostic tests to detect COVID-19 during this global pandemic.”

RDTs using antigen or antibody can quickly yield results within about 10 minutes. Still, their accuracy is significantly low at 50-70 percent of that of molecular genetic tests, they said.

“Due to false results, an infected patient could freely move around without a diagnosis and transmit the virus to others, or a healthy person could be hospitalized for no reason, waste medical supplies, and become vulnerable to unnecessary infection risks, causing grave social confusion,” they said.

Korea has already established a system for massive molecular genetic tests, capable of conducting 15,000 to 25,000 PCR tests, and the accurate testing needs only about six hours, the statement said. “At this moment, Korea does not need to introduce RDTs.”

soo331@docdocdoc.co.kr

<© Korea Biomedical Review, All rights reserved.>

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