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Rapid Covid tests miss 90% of asymptomatic cases

nature.com

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Re: Rapid Covid tests miss 90% of asymptomatic cases

#11

Post by dathinab »

api wrote: post #3

Don't these have lower viral load? So it's really a sensitivity issue, which isn't that surprising for a cheap rapid test.

yes, it's also a well known limitation which has been discussed a lot in the past _when they where introduced_.

Basically the argument is: "if the test misses it, then in most situations the viral load is low enough to have a limited risk for other people"

The only gotcha people tend to forget: The viral load can change over time, which means they are only useful for a few hours not a full day.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#12

Post by whywhywhywhy »

henry-j wrote: post #5

Referenced paper: https://doi.org/10.7326/M23-0385 Not much behind the paywall of the article OP linked: “Rapid antigen tests are much more reliable at detecting COVID-19 in people with symptoms than in those without, finds the largest study to compare home rapid tests with gold-standard PCR tests1. Apurv Soni at the UMass Chan Medical School in Worcester, Massachusetts, and his colleagues, followed 5,353 initially u…

>The authors say that an informational campaign about the proper way to take rapid tests might help to preserve public confidence in the tests’ utility.”

Why do we have to spend tax payer money for a campaign to try and force people to care about the utility of a product that can't accurately detect a symptomless virus.

Honestly starting to forget it was ever even a thing.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#13

Post by throwawaaarrgh »

40-50% of cases are asymptomatic, so the tests are still good at confirming if a symptom is COVID-19. By taking 3 tests over time the odds of detection are better.

But almost everyone has stopped wearing masks, so for those people, testing is pointless anyway. It would be like putting a lock on your own firearm, and then wandering naked across a firing range.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#15

Post by elif »

I think a big part of this is the mixed (lack of?) messaging regarding when is the optimal time to test after a potential exposure.

I've known people who tested the day after and considered themselves 'in the clear', and even my day 3 + day 4 strategy is based upon averages I had to pull from papers on disparate or ambiguous variants.

IMO this kind of heuristic should be printed on the packaging.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#16

Post by BoxFour »

Symmetry wrote: post #8

Duh, they only detect levels of viral load sufficient to make a person infectious, around 1e6 RNA copies per cc of fluid. And viral load tends to peak somewhere in the 1e10 to 1e14 range, people at 1e6 really have to work at coughing directly on to growth plates to create a sample. Back in the early days of Covid-19 people didn't typically begin displaying symptoms visible without an x-ray until they'd nearly reach t…

Indeed, it appears that this is somewhat redundant.

A majority, if not all, of the rapid tests I have used explicitly caution against taking one in the absence of symptoms, as it is expected to yield negligible results.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#17

Post by billsmithaustin »

whywhywhywhy wrote: post #12
henry-j wrote: post #5

Referenced paper: https://doi.org/10.7326/M23-0385 Not much behind the paywall of the article OP linked: “Rapid antigen tests are much more reliable at detecting COVID-19 in people with symptoms than in those without, finds the largest study to compare home rapid tests with gold-standard PCR tests1. Apurv Soni at the UMass Chan Medical School in Worcester, Massachusetts, and his colleagues, followed 5,353 initially u…

>The authors say that an informational campaign about the proper way to take rapid tests might help to preserve public confidence in the tests’ utility.” Why do we have to spend tax payer money for a campaign to try and force people to care about the utility of a product that can't accurately detect a symptomless virus. Honestly starting to forget it was ever even a thing.

I had COVID a few weeks ago. You will remember.

Re: Rapid Covid tests miss 90% of asymptomatic cases

#18

Post by taf2 »

I feel like... "90 of statistics are made up" quote applies here... not seeing much in terms of convincing evidence...

- https://www.goodreads.com/quotes/70193-over-85-of-all-statis... - https://www.businessinsider.com/736-of-all-statistics-are-ma... - https://www.quora.com/Someone-once-said-that-98-of-all-stati...

Re: Rapid Covid tests miss 90% of asymptomatic cases

#20

Post by jefftk »

kozinc wrote: post #4

BTW, what does this even mean: "But if the tests work much better when taken three times over the course of several days."

The tests are much more likely to successfully diagnose you if you take them near your peak viral load. Multiple tests over several days gives you more chances to sample near that peak.
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