Thread by @bopinion

Until a vaccine arrives, the world has to find a way to live with Covid-19 and without lockdowns.

One approach with promise? Mass testing with new tests that deliver near-instant results bloom.bg/3eBKBlk

🇸🇰Slovakia used rapid diagnostic tests on 3.6 million people -- two-thirds of its population -- in just two days.

Now Boris Johnson wants to try it in the U.K., starting with a trial in Liverpool bloom.bg/3eBKBlk

The northern English City is offering all residents and workers a rapid antigen test.

Some 2,000 military personnel have been brought in to help out. If it goes well, millions of the tests will be distributed to other regions before Christmas bloom.bg/3eBKBlk

Rapid antigen tests:

💰 Are cheaper than PCR tests
👶🏽 Use the same technology as pregnancy tests
⏱Give results in 15-30 minutes

Their main drawback? Accuracy bloom.bg/3eBKBlk

The test being used in Liverpool is reported to correctly identify:

➡️People who don’t have Covid 99.9% of the time
➡️People with Covid 96% of the time

That’s a lot of people being wrongly told they don’t have the virus bloom.bg/3eBKBlk

One complaint is that Johnson’s plans seem to be asking more of the test than it was designed for. The test is intended for symptomatic people within the first 5 days of those symptoms.

But Johnson is encouraging everyone to get tested, symptoms or not bloom.bg/3eBKBlk

.@deeksj, a professor of biostatistics, says:

“If you're using these tests to see whether your rugby team is safe to play with each other and you are missing cases, then you suddenly end up with a rugby team that is sick” bloom.bg/3eBKBlk

Some scientists argue that if testing is widespread enough and repeated regularly, lower accuracy is not a problem.

One study suggested rapid tests could save tens of thousands of lives in the U.S. and boost GDP even at lower levels of accuracy bloom.bg/3eBKBlk

Using a standard PCR test to confirm (at least some of) the antigen test results would establish a more accurate picture of who has the virus, especially among asymptomatic people.

Unfortunately, there are no plans to employ such an approach in Britain bloom.bg/3eBKBlk

Mass testing is no silver bullet: It requires the support of a strong program of regular testing, contact tracing and isolation.

But, done properly, it could be a game-changer bloom.bg/3eBKBlk