Thread: Coronavirus
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Old 25.01.2021, 18:54
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Re: Coronavirus

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I am not sure how to interpret these numbers. The tests are not 100% accurate, so the more Covid prevalence drops, the more we will see a lot of false positive results from 55'000 tests. For example, if the test is 95% accurate (sensitive), and the disease prevalence is only 1%, then testing 55k people will give us over 3000 positives, and around 85% of these positives will be false.
We don't know exactly how accurate the tests are, but we might never get to small number of cases simply because we are testing a lot of people.
There is random community testing and there is targeted testing of individuals that have symptoms. It seems logical that those who have symptoms are more likely to return a true positive, and not a false positive result.

Here's a BBC article from October that gets into it a bit more
https://www.bbc.com/news/54270373

One paragraph of note, emphasis mine:
Quote:
Figures for late September from Public Health England show that 7% of community tests were positive. That means of every 1,000 people tested, 70 were positive. Even with a false positive rate of 0.8%, seven of those would be false positives, but 63 would be true positives - the vast majority.

So the daily case count is not being skewed significantly by false positives. There will also be some false negatives, meaning that some people who actually have Covid are not being counted.
It's not clear from the data I've seen how many of the tests in Switzerland are community tests as opposed to tests of people who have symptoms. That would be interesting to know.
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