Coronavirus: One test may be insufficient.

The CDC has been slow in making coronavirus tests available. Weeks after the virus broke, they finally seem to be ramping up.

But now it appears that a single test may not be enough to detect the virus. Per an online University of California San Francisco (UCSF) publication:

The currently available diagnostic test is a PCR test developed by the CDC, which looks for RNA from the virus. However, hospitalized patients infected with the new coronavirus can have test results that vary from day to day because the amount of virus produced by the body can change throughout the course of the illness, said Chiu.

Repeat testing may be necessary to determine if a suspected person has been infected or when a patient is no longer infectious. “The take home message is that a test that looks at a single time point is not sufficient to rule out infection,” said Chiu.

Medicine Net reports even more sobering news, stating that infected individuals can have multiple negative tests before one finally comes back positive:

Reports suggest some people test negative up to six times even though they are infected with the virus, according to the BBC and Chinese media. Such was the case with Dr. Li Wenliang, the ophthalmologist who first identified the outbreak and was reprimanded by Chinese authorities when he tried to warn others.

Dr. Wenliang developed a cough and fever after unknowingly treating an infected patient. He was hospitalized, testing negative for coronavirus several times before eventually receiving a positive result. On Jan. 30 the doctor posted: "Today nucleic acid testing came back with a positive result, the dust has settled, finally diagnosed," according to the BBC. Dr. Wenliang passed away on February 7 in Wuhan, the epicenter of the outbreak.

False-negative test results…cause several problems. Patients may be turned away from hospitals and medical facilities when they require care. They may infect others…Patients' conditions may also worsen without treatment.

When faced with a highly infectious, potentially deadly pathogen, even a small number of false negatives can have a potentially serious and widespread impact on the larger population.

In one study, 3% of participants had false negatives. That may seem like a small number, but if you extrapolate from that, the number of people who can then unknowingly infect others is significant. It also means that a portion of the population who are infected wouldn’t receive the medical care they need.

There appear to be multiple reasons why an infected person can test negative, including lab error, insufficient sample, improperly handled or stored samples, patients being tested too early in disease progression, and fluctuation in viral levels over the course of the illness. In addition, the CDC had serious problems with test kits that were initially provided that had faulty reagents in the testing solution.

So how do we combat these myriad challenges to ensure we get accurate results and limit the spread of this virus?

Recommendations include repeat testing, lung imaging, and isolation of suspected cases. Testing is critical since diagnosis based on clinical symptoms alone could result in misdiagnoses or overdiagnoses, especially because symptoms often mimic the common cold or flu.

In addition, we need consistency around the world regarding how people are diagnosed and agreement on what defines a confirmation of coronavirus. This is the only way we can close to knowing the true number of those infected.

In light of this information, I take cold comfort in recent announcements about increasing availability of testing in the United States. Yes, we must be able to test more rather than less. But the results must be reliable, and it appears a single test may result in a lot of people slipping through the cracks.

The CDC has been slow in making coronavirus tests available. Weeks after the virus broke, they finally seem to be ramping up.

But now it appears that a single test may not be enough to detect the virus. Per an online University of California San Francisco (UCSF) publication:

The currently available diagnostic test is a PCR test developed by the CDC, which looks for RNA from the virus. However, hospitalized patients infected with the new coronavirus can have test results that vary from day to day because the amount of virus produced by the body can change throughout the course of the illness, said Chiu.

Repeat testing may be necessary to determine if a suspected person has been infected or when a patient is no longer infectious. “The take home message is that a test that looks at a single time point is not sufficient to rule out infection,” said Chiu.

Medicine Net reports even more sobering news, stating that infected individuals can have multiple negative tests before one finally comes back positive:

Reports suggest some people test negative up to six times even though they are infected with the virus, according to the BBC and Chinese media. Such was the case with Dr. Li Wenliang, the ophthalmologist who first identified the outbreak and was reprimanded by Chinese authorities when he tried to warn others.

Dr. Wenliang developed a cough and fever after unknowingly treating an infected patient. He was hospitalized, testing negative for coronavirus several times before eventually receiving a positive result. On Jan. 30 the doctor posted: "Today nucleic acid testing came back with a positive result, the dust has settled, finally diagnosed," according to the BBC. Dr. Wenliang passed away on February 7 in Wuhan, the epicenter of the outbreak.

False-negative test results…cause several problems. Patients may be turned away from hospitals and medical facilities when they require care. They may infect others…Patients' conditions may also worsen without treatment.

When faced with a highly infectious, potentially deadly pathogen, even a small number of false negatives can have a potentially serious and widespread impact on the larger population.

In one study, 3% of participants had false negatives. That may seem like a small number, but if you extrapolate from that, the number of people who can then unknowingly infect others is significant. It also means that a portion of the population who are infected wouldn’t receive the medical care they need.

There appear to be multiple reasons why an infected person can test negative, including lab error, insufficient sample, improperly handled or stored samples, patients being tested too early in disease progression, and fluctuation in viral levels over the course of the illness. In addition, the CDC had serious problems with test kits that were initially provided that had faulty reagents in the testing solution.

So how do we combat these myriad challenges to ensure we get accurate results and limit the spread of this virus?

Recommendations include repeat testing, lung imaging, and isolation of suspected cases. Testing is critical since diagnosis based on clinical symptoms alone could result in misdiagnoses or overdiagnoses, especially because symptoms often mimic the common cold or flu.

In addition, we need consistency around the world regarding how people are diagnosed and agreement on what defines a confirmation of coronavirus. This is the only way we can close to knowing the true number of those infected.

In light of this information, I take cold comfort in recent announcements about increasing availability of testing in the United States. Yes, we must be able to test more rather than less. But the results must be reliable, and it appears a single test may result in a lot of people slipping through the cracks.