Mystery in Wuhan: recovered coronavirus patients test negative then positive
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Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive
#2Couple of thoughts:
- I think we need to know a LOT more about the sensitivity, specificity, and accuracy of every test that's being deployed right now. I am 100% willing to believe that "testing negative and then positive" means "you have a pretty low viral load and our tests suck more than we're willing to admit out loud right now".
- I think we need to be very clear that there are two kinds of tests: "you have an active SARS-CoV-2 infection right now, and also "you have once had a SARS-CoV-2 infection in the semi-recent past". One tells you who needs care, one tells you who is at least temporarily immune we hope.
Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive
#3Favorite line from the article:
"In terms of those who retested positive, the official party line is that they have not been proven to be infectious. That is not the same as saying they are not infectious," one of the Wuhan doctors who tested positive twice told NPR [...] "If they really are not infectious," the doctor said, "then there would be no need to take them back to the hospitals again."
So why are the asymptomatic cases required to quarantine under medical observation for 14 days but not counted?
Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive
#4Couple of thoughts: - I think we need to know a LOT more about the sensitivity, specificity, and accuracy of every test that's being deployed right now. I am 100% willing to believe that "testing negative and then positive" means "you have a pretty low viral load and our tests suck more than we're willing to admit out loud right now". - I think we need to be very clear that there are two kinds of tests: "you have an…
The article mentions RNA implying that this is the PCR test not an Antibody test. False positives exist with the PCR test. Information I could find suggests the primary cause is sample contamination. So running the test multiple times through different labs and clinicians is an obvious workaround.
Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive
#5Favorite line from the article: "In terms of those who retested positive, the official party line is that they have not been proven to be infectious. That is not the same as saying they are not infectious," one of the Wuhan doctors who tested positive twice told NPR [...] "If they really are not infectious," the doctor said, "then there would be no need to take them back to the hospitals again." So why are the asympt…
"Not proven to be infectious" and "proven to not be infectious" aren't the same thing. Quarantine/observation is warranted for the first.
Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive
#6Czechia got some quick tests from China. Their reliability was about 60% compared to lab, false positives and false negatives.
I think DNA and RNA research is severely lacking in most countries. In a few years we will look at this year as 1960ies of computer engineering.
Edit: source https://www.irozhlas.cz/zpravy-domov/ostrava-rychlotesty-kor...
Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive
#7Couple of thoughts: - I think we need to know a LOT more about the sensitivity, specificity, and accuracy of every test that's being deployed right now. I am 100% willing to believe that "testing negative and then positive" means "you have a pretty low viral load and our tests suck more than we're willing to admit out loud right now". - I think we need to be very clear that there are two kinds of tests: "you have an…
The article mentions RNA implying that this is the PCR test not an Antibody test. False positives exist with the PCR test. Information I could find suggests the primary cause is sample contamination. So running the test multiple times through different labs and clinicians is an obvious workaround.
Surely this is not a false-positive, but rather a false-negative?
That is, the patients were observed clinically to have caught and recovered from the virus, yet the test shows no trace of the viral infection.
Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive
#8Couple of thoughts: - I think we need to know a LOT more about the sensitivity, specificity, and accuracy of every test that's being deployed right now. I am 100% willing to believe that "testing negative and then positive" means "you have a pretty low viral load and our tests suck more than we're willing to admit out loud right now". - I think we need to be very clear that there are two kinds of tests: "you have an…
In general PCR tests are highly sensitive. Even smallest viral loads can be detected
(Edit) added in general above due to valid points in the comments below
Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive
#9Couple of thoughts: - I think we need to know a LOT more about the sensitivity, specificity, and accuracy of every test that's being deployed right now. I am 100% willing to believe that "testing negative and then positive" means "you have a pretty low viral load and our tests suck more than we're willing to admit out loud right now". - I think we need to be very clear that there are two kinds of tests: "you have an…
In general PCR tests are highly sensitive. Even smallest viral loads can be detected (Edit) added in general above due to valid points in the comments below
if:
- you do them right
- your reagents are good
- the kit was assembled properly
- there's no contamination in the machines
- you got a good sample
- ...
The capability for a highly sensitive and accurate test in no way guarantees that a randomly sampled administration of that test is going to meet the high standard that the test may be capable of.
Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive
#10Couple of thoughts: - I think we need to know a LOT more about the sensitivity, specificity, and accuracy of every test that's being deployed right now. I am 100% willing to believe that "testing negative and then positive" means "you have a pretty low viral load and our tests suck more than we're willing to admit out loud right now". - I think we need to be very clear that there are two kinds of tests: "you have an…
In general PCR tests are highly sensitive. Even smallest viral loads can be detected (Edit) added in general above due to valid points in the comments below
The PCR can detect if there is virus in the swab. But the swab may not have scooped up any virus even though the person had some.