4 ms·

96% sensitivity rate for people with symptoms. 91% sensitivity rate without symptoms. Given the ramp of virus replication between the time that one is asymptoma

by ttul 6y ago

96% sensitivity rate for people with symptoms. 91% sensitivity rate without symptoms. Given the ramp of virus replication between the time that one is asymptomatic and when one is infectious (ie hours), this sensitivity rate is excellent for an at-home test. Imagine if such a test had been available to everyone nine months ago. The pandemic could have been effectively ended.

noneeeed 6y ago
Interesting, this seems much better than the "lateral-flow" tests that we've started using in the UK for mass community testing. Apparantly those are only detecting about 50% of positive cases (not sure what the symptomatic/asymptomatic breakdown is). 90-95% sensitivity will be a real game changer.
- novok 6y ago
  There is a math that you have to apply with the amount infected. Like a test that is %99 accurate for a disease that only happens %0.001 of the time will have high false negative or positive rate, which is somewhat unexpected result. More detail: https://www.lesswrong.com/posts/XTXWPQSEgoMkAupKt/an-intuitive-explanation-of-bayes-s-theorem https://www.lesswrong.com/posts/XTXWPQSEgoMkAupKt/an-intuiti...
mrlala 6y ago
Eh not for $30 a pop though.. it's not like you take it once and say "Yay I don't have it! back to normal!".
- mlyle 6y ago
  Testing once per week is $4 per day, which definitely adds up. But if you do this testing staggered across a population, you interrupt a whole lot of transmission chains. Not to mention a whole lot of the $30 is the disposable bluetooth scanner. If you wanted to do this kind of antigen test repeatedly at the population level you'd make different choices.
  - imaginenore 6y ago
    > you interrupt a whole lot of transmission chains Trees! Know your data structures. /s
- TravisLS 6y ago
  We in the US spent something like $7000/citizen on stimulus so far though, so $30/test gets you a lot of tests if it mitigates the economic effects of the virus.
- deleted 6y ago
  [deleted]
fastball 6y ago
What about specificity?
- ttul 6y ago
  98% specificity. This comes from the FDA's information sheet on the Lucira test: https://www.fda.gov/media/143809/download https://www.fda.gov/media/143809/download Interestingly, the Lucira test was 100% sensitive for all samples that had a PCR CT value of < 37.5 (n=45). The CT value is the number of times that the PCR test has to amplify (i.e. make copies of) the genetic material in the sample before there was enough material that it produced a positive test result. A low CT value means that there is a lot of viral RNA present; a high CT value means the opposite. A CT value of 37.5 is exceptionally high; it corresponds to about 10 copies of virus per microliter. Someone only becomes infectious (it's believed) when the copies per microliter is in the hundreds of thousands. PS don't quote me on the precise numbers here as I am trying to remember them and it's a bit fuzzy. On the information sheet, they say that, "Lucira achieved a 94% positive percent agreement (PPA) and a 98% negative percent agreement (NPA)." Positive agreement is the proportion of comparative/reference method positive results in which the test method result is positive. Negative agreement is the proportion of comparative/reference method negative results in which the test method result is negative.

by ttul 6y ago

noneeeed 6y ago

Interesting, this seems much better than the "lateral-flow" tests that we've started using in the UK for mass community testing. Apparantly those are only detecting about 50% of positive cases (not sure what the symptomatic/asymptomatic breakdown is). 90-95% sensitivity will be a real game changer.

novok 6y ago
There is a math that you have to apply with the amount infected. Like a test that is %99 accurate for a disease that only happens %0.001 of the time will have high false negative or positive rate, which is somewhat unexpected result. More detail: https://www.lesswrong.com/posts/XTXWPQSEgoMkAupKt/an-intuitive-explanation-of-bayes-s-theorem https://www.lesswrong.com/posts/XTXWPQSEgoMkAupKt/an-intuiti...

mrlala 6y ago

Eh not for $30 a pop though.. it's not like you take it once and say "Yay I don't have it! back to normal!".

mlyle 6y ago
Testing once per week is $4 per day, which definitely adds up. But if you do this testing staggered across a population, you interrupt a whole lot of transmission chains. Not to mention a whole lot of the $30 is the disposable bluetooth scanner. If you wanted to do this kind of antigen test repeatedly at the population level you'd make different choices.
- imaginenore 6y ago
  > you interrupt a whole lot of transmission chains Trees! Know your data structures. /s
TravisLS 6y ago
We in the US spent something like $7000/citizen on stimulus so far though, so $30/test gets you a lot of tests if it mitigates the economic effects of the virus.
deleted 6y ago
[deleted]

fastball 6y ago

What about specificity?

ttul 6y ago
98% specificity. This comes from the FDA's information sheet on the Lucira test: https://www.fda.gov/media/143809/download https://www.fda.gov/media/143809/download Interestingly, the Lucira test was 100% sensitive for all samples that had a PCR CT value of < 37.5 (n=45). The CT value is the number of times that the PCR test has to amplify (i.e. make copies of) the genetic material in the sample before there was enough material that it produced a positive test result. A low CT value means that there is a lot of viral RNA present; a high CT value means the opposite. A CT value of 37.5 is exceptionally high; it corresponds to about 10 copies of virus per microliter. Someone only becomes infectious (it's believed) when the copies per microliter is in the hundreds of thousands. PS don't quote me on the precise numbers here as I am trying to remember them and it's a bit fuzzy. On the information sheet, they say that, "Lucira achieved a 94% positive percent agreement (PPA) and a 98% negative percent agreement (NPA)." Positive agreement is the proportion of comparative/reference method positive results in which the test method result is positive. Negative agreement is the proportion of comparative/reference method negative results in which the test method result is negative.