Everyone is talking about the importance of more extensive COVID-19 testing in determining who is infected, and (eventually) who has been infected.
But nearly all the discussion that I've heard and read has been based on the assumption that the relevant tests are accurate. And this assumption is false — the available tests for this condition seem to be even less accurate than medical tests generally are. Thus Saurabh Jha, "False Negative: COVID-19 Testing's Catch-22", Medpage Today 3/31/2020:
In a physician WhatsApp group, a doctor posted he had a fever of 101 degrees Fahrenheit and muscle ache, gently confessing that it felt like his typical "man flu" which heals with rest and scotch. 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 assumes he's infected and quarantine for two weeks, with a bottle of scotch.
It's believed that the secret sauce to fighting the pandemic is testing for the virus. The depth of the response will be different if 25% of the population is infected than 1%. Testing is the third way, rejecting the choice between death and economic depression. Without testing, strategy is faith-based. But 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. The Chinese ophthalmologist who originally sounded the alarm about coronavirus, Li Wenliang, had several negative tests. He died from the infection.
In one study, RT-PCR's sensitivity – that's the percentage of infected testing positive – was 70%. Of 1,000 with coronavirus, 700 test positive but 300 test negative.
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