Thread by @statesdj

Let’s talk testing, specifically the coronavirus test we really need and essentially no one is talking about. What we need is a fast, low cost field test for highly contagious people, and tests like this exist, in fact they’ve been around quite a while
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Full disclosure. I am an exec in a biotech company, and my company is developing tests for SARS-CoV-2. I try to keep my posts objective, but obviously I believe that this is an important issue and that the solutions we are pursuing have merit
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People are contagious for COVID-19 before they develop symptoms, and the number of virus shed varies dramatically from person to person and for any given person from day to day. This makes testing a challenge
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nature.com/articles/s4159…

There are COVID-19 superspreaders, people who infect many other people. We assume they shed a very high viral burden although this hasn’t been proven. To stop viral spread, we really need to identify and isolate superspreaders
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thelancet.com/journals/lance…

The amount of virus being shed by different people varies enormously. The widely used RT-PCR test turns positive anywhere between cycle 15 and cycle 37. That’s more than a million fold difference in viral load!
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Because asymptomatic people can be contagious and viral shedding varies from day to day, we need to test frequently. We’d really like to be able to test everyone coming in to work every day at the beginning of their shift
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So how do we make a fast, low cost field test for SARS-CoV-2? We adapt a proven technology like the home pregnancy test, technically known as a lateral flow chromatography assay
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en.wikipedia.org/wiki/Lateral_f…

Lateral flow assays work by letting a sample of bodily fluid, e.g. saliva or urine, diffuse through a system where the particle of interest is tagged and detected. In a pregnancy test that particle is beta-HCG. For coronavirus, it’s the virus
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What do we need to setup a lateral flow assay? Two different binding domains each of which binds the target. One to tag it and a second to trap it, and they need to bind to separate sites so they don’t interfere with each other
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Antibodies are great candidates for the binding domains. In fact, all of the people who have recovered from COVID-19 have pretty good antibodies against the virus in their plasma. That’s why we give convalescent plasma as treatment
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One way to get binding domains is to clone the antibody genes from the B cells of a person who has recovered from COVID-19, find clones that bind tightly and express them as monoclonal antibodies
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A test like this is really cheap to make. You only need a tiny amount of antibody per test and the rest of the kit is inexpensive plastic and a few chemicals. These tests are quick, and they don’t require fancy equipment to run
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In fact, tests just like this have been used to test for influenza! So why did we shift to RT-PCR? RT-PCR is more sensitive and maybe more specific, but it’s a lot more expensive to run and requires a fancy instrument.
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But to detect contagious people with SARS-CoV-2, we don’t need the ultimate sensitivity. People shedding only a very small number of virus probably aren’t all that contagious. It’s the folks shedding massive viral counts that we really need to catch
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We need to mass produce these test kits so that people can test themselves at home and employers can test workers to keep job sites safe, and they can do so as often as they like, even every day. It’s possible and we’re working on it.
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By the way, I’m not the only one thinking this way. Bill Gates agrees with me. Nice company to have
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washingtonpost.com/opinions/2020/…