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Mystery in Wuhan: recovered coronavirus patients test negative then positive

npr.org

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Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive

#31

Post by gojomo »

The journalists here haven't mentioned what kinds of tests each the 4 unnamed sources – 2 doctors, 2 citizens – had at each stage of their 'positive then negative then positive again' journey. They haven't mentioned if any of the individual tests were followed-up with multiple confirmatory tests of alternate methods.

To the extent they mention test types at all, it is quotes from "February" or "a professor... by email" – nothing about these persons' tests.

Yet, the tests in use have some level of false-positive and false-negative. Some variants have had quite high error rates – which may still be acceptable for mass-screening, but not for understanding the course of a single person's infection status.

So, among many millions of people tested in China, a handful have had alternating results not correlated with their symptoms? Not a surprise, even with tiny test error rates, unless each contributing result to the "+/-/+" pattern was reconfirmed by multiple-tests/multiple-methods.

(Note this also suggests many accounts of 'asymptomatic cases' may just be false-positives who never had Covid-19.)

Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive

#32

Post by Vysero »

gentleman11 wrote: post #23

> They all requested anonymity when speaking with NPR because those who have challenged the government's handling of the outbreak have been detained. We need to be more hesitant to praise their pandemic response

My thoughts exactly

Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive

#33

Post by omnipugent »

baxtr wrote: post #8
hprotagonist wrote: post #2

Couple 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

Can't PCR tests detect damaged RNA and report that as a positive?

https://www.aim-med.org/hiv-rna-test/

Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive

#34

Post by canada_dry »

When you factor in this news: https://www.theguardian.com/film/2020/mar/27/china-re-closes... It would certainly appear that this virus is not yet finished with China.

More importantly, it would seem that premature lifting of restrictions is done at our peril.

Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive

#35

Post by stevespang »

False Positives. This would be the first time in history that a sizeable number of those "cured" of a virus where actually shedding live virus ? Depending on the type of test, it can read antibodies to the virus from those "cured", which gives a false positive.

Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive

#36

Post by samsonradu »

lopis wrote: post #19
dmix wrote: post #16

Earlier quoted context omitted.

Sounds like a test from a single Chinese company and the results were closer to 30% accurate: > The Chinese Embassy in Spain said that the Bioeasy tests were not part of China's medical donations and that the firm didn't have a license to sell its products.

30% accurate? Does that mean it's better to believe the opposite of what the test says most of the time?

Then it would be 70% accurate

Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive

#37

Post by gojomo »

hinkley wrote: post #28
twic wrote: post #12

Earlier quoted context omitted.

And if you swabbed an infected part of the body in the first place! In 205 patients with proven COVID-19 [...] bronchoalveolar lavage fluid was positive in 14/15 (93%), sputum 75/104 (72%), nasal swabs 5/8 (63%), brush biopsy 6/13 (46%), pharyngeal swabs 126/398 (32%), feces 44/153 (29%), blood 3/307 (1%), and urine 0/72 (0%). https://www.jwatch.org/na51116/2020/03/17/pharyngeal-and-nas...

Hol' up. > blood 3/307 (1%) Why isn't their blood rotten with virus?

I suspect it's because this virus is optimized to enter cells that line the lungs/respiratory tract, then also sheds back that same way. Meanwhile, cells in, and along, the bloodstream aren't infected – and are most-trafficked by the body's immune response, including virus-destroying antibodies.

(Why are rodents more prevalent in the walls/crawlspaces of a dwelling, rather than the hallways?)

Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive

#38

Post by seraphsf »

hinkley wrote: post #28
twic wrote: post #12

Earlier quoted context omitted.

And if you swabbed an infected part of the body in the first place! In 205 patients with proven COVID-19 [...] bronchoalveolar lavage fluid was positive in 14/15 (93%), sputum 75/104 (72%), nasal swabs 5/8 (63%), brush biopsy 6/13 (46%), pharyngeal swabs 126/398 (32%), feces 44/153 (29%), blood 3/307 (1%), and urine 0/72 (0%). https://www.jwatch.org/na51116/2020/03/17/pharyngeal-and-nas...

Hol' up. > blood 3/307 (1%) Why isn't their blood rotten with virus?

Because it’s a respiratory disease

Re: Mystery in Wuhan: recovered coronavirus patients test negative then positive

#40

Post by Spooky23 »

hprotagonist wrote: post #2

Couple 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…

Even a common well established test like a quick strep test has a significant (10% iirc) false negative rate. I'm sure that a rapidly developed test to an emerging target is going to have a significant error rate.
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