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Tag: RT-PCR

False Negative: Testing’s Catch-22

By SAURABH JHA, MD

In a physician WhatsApp group, a doctor posted he had fever of 101° F and muscle ache, gently confessing that it felt like his typical “man flu” which heals with rest and scotch. Nevertheless, he worried that he had coronavirus. When the reverse transcription polymerase chain reaction (RT-PCR) for the virus on his nasal swab came back negative, he jubilantly announced his relief. 

Like Twitter, in WhatsApp emotions quickly outstrip facts. After he received a flurry of cheerful emojis, I ruined the party, advising that despite the negative test he assume he’s infected and quarantine for two weeks, with a bottle of scotch. 

It’s conventional wisdom that the secret sauce to fighting the pandemic is testing for the virus. To gauge the breadth of the response against the pandemic we must know who and how many are infected. The depth of the response will be different if 25% of the population is infected than 1%. Testing is the third way, rejecting the false choice between death and economic depression. Without testing, strategy is faith-based. 

Our reliance on testing has clinical precedence – scarcely any decision in medicine is made without laboratory tests or imaging. Testing is as ingrained in medicine as the GPS is in driving. We use it even when we know our way home. But tests impose a question – what’ll you do differently if the test is negative? 

That depends on the test’s performance and the consequences of being wrong. Though coronavirus damages the lungs with reckless abandon, it’s oddly a shy virus. In many patients, it takes three to four swabs to get a positive RT-PCR. The Chinese ophthalmologist, Li Wenliang, who originally sounded the alarm about coronavirus, had several negative tests. He died from the infection.

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CDC Laboratory Guidance on Ebola

Tom Frieden optimizedFor more than four decades, Ebola virus had only been diagnosed in central or eastern Africa.

Then late this past March, the first cases of Ebola began appearing in a surprising part of the continent. The Ministry of Health in Guinea notified WHO of a rapidly evolving outbreak of Ebola virus disease. The outbreak in Guinea was the first sign the virus had made the jump across the continent.

Ebola then spread quickly to Sierra Leone and Liberia, and then to Nigeria.

As the world learned of the cases, CDC began receiving questions from American hospital labs. They were looking for guidance on how to handle testing for patients who had recently returned to the U.S. from West Africa with potential Ebola symptoms.

If U.S. hospitals were to run laboratory tests on these patients, how could they be sure their staff could safely handle materials that might contain this dangerous virus? Did they need the kind of personal protective equipment they saw CDC scientists using when they were testing for Ebola?

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