
Mystery in Wuhan: recovered coronavirus patients test negative then positive - ceejayoz
https://www.npr.org/sections/goatsandsoda/2020/03/27/822407626/mystery-in-wuhan-recovered-coronavirus-patients-test-negative-then-positive
======
eanzenberg
Literally false positive and false negatives. In other words, if you test
millions of people, there will be more people tested positive who DON'T have
the disease vs. those who test positive and HAVE the disease.

~~~
devy
Exactly! For any medical tests, there are 2 measurements: sensitivity and
specificity, one to judge false positive and another judge the false
negatives.

[https://en.wikipedia.org/wiki/Sensitivity_and_specificity](https://en.wikipedia.org/wiki/Sensitivity_and_specificity)

~~~
AzzieElbab
Spain sent testkits back to China because they were unreliable

~~~
tehjoker
In the NYT article on Italy today, frontline medics were saying that clinical
symptoms were anecdotally more reliable than the tests because there are too
many false negatives. Not sure whose tests they're using but I've heard
similar things about US PCR tests.

[https://www.nytimes.com/interactive/2020/03/27/world/europe/...](https://www.nytimes.com/interactive/2020/03/27/world/europe/coronavirus-
italy-bergamo.html?action=click&module=Spotlight&pgtype=Homepage)

~~~
devy
Yep! CT scans and clinician's experience is more reliable than any tests for
COVID-19 diagnostics (which should only serving as a definitive confirmation).
This also why I believe human doctors are still unbeatable by AI

~~~
dirtyid
I remember an article early in the outbreak that Chinese doctors found the
most reliable diagnosis comes from CT scans. Test was merely the first filter.
They tuned the settings to increase scan speed at the cost of resolution and
setup a process to scan up to 200 patients a day per scanner. I wonder if this
is still best practice that other countries aren't adopting. On the other hand
I expect tests to have improved since the early days. There's also the
consideration China simply had more CT scanners that could be mobilized to
Wuhan which makes this less practical elsewhere.

~~~
tehjoker
My doctor friend who got the minutes of a call with a chinese doctor said they
were also swabbing multiple areas of the body for PCR and doing an antibody
screen as well (in addition to CT).

------
cs702
My key takeaway after reading this article is that I cannot blindly trust
China's official figures.

NPR reports that "under its newest COVID-19 prevention guidelines, _China does
not include in its overall daily count for total and for new cases those who
retest positive after being released from medical care. China also does not
include asymptomatic cases in case counts_ " (emphasis mine).

One of the Wuhan doctors interviewed for this article told NPR that "I have no
idea why the authorities choose not to count asymptomatic cases in the
official case count. I am baffled."

All doctors and individuals in China who were interviewed for the article
"requested anonymity when speaking with NPR because those who have challenged
the government's handling of the outbreak have been detained."

\--

See also: [https://www.theguardian.com/film/2020/mar/27/china-re-
closes...](https://www.theguardian.com/film/2020/mar/27/china-re-closes-all-
cinemas-over-coronavirus-fears)

------
canada_dry
When you factor in this news:
[https://www.theguardian.com/film/2020/mar/27/china-re-
closes...](https://www.theguardian.com/film/2020/mar/27/china-re-closes-all-
cinemas-over-coronavirus-fears) 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.

------
jankotek
Czechia 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...](https://www.irozhlas.cz/zpravy-domov/ostrava-rychlotesty-
koronavirus_2003231414_sot)

~~~
netvarun
Initially skeptical on your first claim but did find a source:
[https://www.businessinsider.com/coronavirus-spain-says-
rapid...](https://www.businessinsider.com/coronavirus-spain-says-rapid-tests-
sent-from-china-missing-cases-2020-3)
([https://outline.com/uBBJvY](https://outline.com/uBBJvY))

~~~
dmix
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.

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

~~~
samsonradu
Then it would be 70% accurate

~~~
DeonPenny
Agreed the worst test would be 50% accurate

------
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.)

------
nico_h
Favorite 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?

~~~
ceejayoz
"Not proven to be infectious" and "proven to not be infectious" aren't the
same thing. Quarantine/observation is warranted for the first.

~~~
nico_h
Well if you know they are infected, and are worried they might be infectious,
_why not count them_ after all they _are_ occupying a bed.

------
hprotagonist
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 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.

~~~
baxtr
_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

~~~
hprotagonist
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.

~~~
twic
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...](https://www.jwatch.org/na51116/2020/03/17/pharyngeal-and-nasal-swabs-
may-not-have-adequate)

~~~
hinkley
Hol' up.

> blood 3/307 (1%)

Why isn't their blood rotten with virus?

~~~
gojomo
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?)

~~~
hinkley
But the lungs are full of blood, that's how we breath.

So it's spreading mucosally or through connective tissue?

~~~
gojomo
Sure, but if an initially-infected respiratory cell releases its "baby
coronaviruses" out to the respiratory linings, away from the blood, they'll
find lots more of the respiratory cell surfaces they're optimized to infect,
and maybe get a ride out to other hosts on sputum.

To the extent an infected cell releases its "baby coronaviruses" into the
blood stream, they find a hot, chemically active environment – which is
already inhospitable to their continued survival – plus a relative dearth of
the respiratory cell-walls they're optimized to enter, plus a growing number
of hostile antibodies.

(I don't know _if_ a coronavirus-hijacked cell _can_ direct its fresh viruses
one way or the other, but it'd probably prefer to do that if it could, and I
can understand why viruses wouldn't persist long in blood compared to
respiratory-membranes.)

The coronaviruses are definitely active in mucosal surfaces, and carried by
mucus. I haven't seen anything about, nor do I think any activity is
necessarily implied, in other connective tissues.

------
rmu09
Every test in the real world shows false positives and false negatives. I
would expect that doing multiple tests on a massive number of people could
show such results.

------
wangii
as far as I know, cases of 're-positive' have been reported in Chinese
websphere for a while, and there had been doubts and official clarifications:

re-positive report:
[http://www.bjnews.com.cn/feature/2020/03/05/699575.html](http://www.bjnews.com.cn/feature/2020/03/05/699575.html)
(2020/03/05)

expert stance:
[http://www.bjnews.com.cn/news/2020/03/12/702870.html](http://www.bjnews.com.cn/news/2020/03/12/702870.html)
(2020/03/12)

it's about lives and I don't think anyone believe in govt. lightly. so do you.

------
4restm
Med Cram had a segment on this, its believed to be false negatives. As some
the current PCR test are highly inaccurate

------
guscost
Related case report:
[https://www.researchsquare.com/article/rs-17319/v1](https://www.researchsquare.com/article/rs-17319/v1)

------
rurban
This is entirely expected. Ex-positives develop antibodies, so that they are
immune against further infections. Since the virus is so infectious it can
easily lead to further infections, but the antibodies can contain it. Same
happens with flu vaccination. The new PCR tests are so overly precise, that
they can measure the new losing virus cells.

Big question is if the re-positives are infectious again. Doesn't seem to be
plausible, but could be. It's a new virus with a different, stronger header.

------
gentleman11
> 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

~~~
jsight
I don't understand this. I haven't seen "praise"? I have seen realistic
assessments of the ultimate effectiveness, but I see this as vastly different
from "praise".

I think the majority of people in the US that have observed how they handle it
see their approach as overly harsh.

~~~
snapetom
While social media has been more critical depending on the source, the
mainstream media has definitely been carrying the water for China.

[https://twitter.com/KenDilanianNBC/status/124324375891486310...](https://twitter.com/KenDilanianNBC/status/1243243758914863104)

I think it's been interesting wave. When the cases first started, China got
blasted. As it hit the US, Administration political opponents have criticized
the US response, but many have gone to the point of praising China's response
and forgetting about China's actions in December/January.

~~~
wwweston
If China did in fact ship emergency medical supplies to Italy, that's a
gesture worth recognizing and praising. "Carrying water" is a weird way of
characterizing that recognition.

China also deserves criticism; its initial response was dysfunctional in some
ways (albeit somewhat different ways than the United States dysfunctional
response). Fortunately, as you say, it's been blasted in some discussion.

But recognition of ways in which its response has been respectable is less the
mark of someone "carrying water" and more part of the process of learning
things and having our political institutions learn things.

~~~
uncoder0
I've never seen the mainstream media question the veracity of the statistics
about Covid that came out of China until the evidence is too obvious to
ignore. There is plenty of proof that they regularly manipulate their
statistics such as GDP.

[https://www.bloomberg.com/news/articles/2019-03-08/china-
s-g...](https://www.bloomberg.com/news/articles/2019-03-08/china-s-gdp-growth-
pace-was-inflated-for-nine-years-study-finds)

[https://time.com/5811222/wuhan-coronavirus-death-
toll/](https://time.com/5811222/wuhan-coronavirus-death-toll/)

etc

Why should any respectable journalist quote their statistics about COVID and
conclude how effective their response was without mentioning that they've been
known to fabricate statistics? Let alone calling them a 'Global Leader' in
response. I've not seen this qualification mentioned once with respect to
China's stats on this virus.

~~~
dirtyid
>mentioned once

I don't see it frequently in writing, but the majority of TV and podcast
reporting from news sites has the disclaimer. And there's enough China bad
articles out there that I feel like this is implicitly assumed.

Either way, no one trusts Chinese stats, including the Chinese public
themselves, and the Chinese government most of all. The ability to collect
accurate statistics when there's so many different development levels country-
wide simply isn't there. For example, China doesn't use GDP internally, they
use LKI, LiKeQiang Index which aggregates a value from measurable indicators
like freight cargo volume, electric consumption, bank loans. There's also TSF,
Total Social Financing. They can still be gamed, but physically (running empty
trains), but much harder to fake via submitting fake excel sheets to central
government. Chinese GDP is basically a back of the napkin estimate to appease
foreign investors, it's also used to set growth targets instead of reflecting
it. Most of the mainstream western reporting on Chinese GDP does not
understand this. It's well understood among China watchers. The most
comprehensive study on Chinese GDP so far, by CSIS, suggested China was under
reporting their GDP.

As for stacked urns in Wuhan, the city is still under quarantine so urns would
not be picked up. Also necessary to account for other sources of death. The
article quotes 56K cremations in Q4 2019, so a few thousands urns especially
as restock doesn't seem atypical. Like LKI, it's an useful oblique indicator,
but should be considered in other context. If there's mass death, enough to
measurably affect hysterical people in quarantine, it would be on Chinese
social media which would leak to China watchers. There's many expats and
Chinese people with VPNs, things that affect the public on a mass scale
inevitably leaps over the firewall, it's not opaque like politburo politics.
People need to stop looking at Chinese numbers and instead extrapolate from
oblique indicators. When expats in China talk about things returning to
normal, when Chinese diaspora aren't mourning about sick or dead family
members en-mass, then you can assume that reflects ground reality.

------
m0zg
Here's probably why:
[https://www.theguardian.com/world/2020/mar/27/coronavirus-
te...](https://www.theguardian.com/world/2020/mar/27/coronavirus-test-kits-
withdrawn-spain-poor-accuracy-rate)

------
dang
A similar thread from 10 days ago:
[https://news.ycombinator.com/item?id=22608676](https://news.ycombinator.com/item?id=22608676)

------
DeonPenny
You've locked healthy people inside with sick people during the quarantine.
Wouldn't that cause some reinfections? After your immune system got beat down
the first time.

~~~
cjbprime
Catching a virus normally provides you immunity for some time frame from three
months up to years or forever. We aren't expecting reinfection (yet) because
we're expecting immunity, but might be wrong.

------
anotheryou
Of 6 people I know with corona 2 tested negative despite showing the same
symptoms as their positive partners...

I think it's just false negatives.

------
grugagag
Related:

[https://www.bloomberg.com/news/articles/2020-03-27/stacks-
of...](https://www.bloomberg.com/news/articles/2020-03-27/stacks-of-urns-in-
wuhan-prompt-new-questions-of-virus-s-toll)

China is likely hiding the real numbers for unknown reasons

~~~
robocat
The “stacks of urns” can almost be answered by the quote from the article:
“There were 56,007 cremations in Wuhan in the fourth quarter of 2019”. (Edit:
I shortened quote).

After a month of lockdown, the number of backlogged urns should be over 18000.

~~~
oefrha
(More than) two months of lockdown, not one. So ~38000 cremations “normally”.
Spread out to eight funeral homes, you’d expect 4k-5k at each location. (Since
people were allegedly locked into apartments or at least apartment complexes,
apparently they weren’t picking up ashes until now.) So “thousands” at each
location tells us precious nothing.

Article is intentionally misleading, burying the “normal” stats that way.

------
m3kw9
But they were not found to shed viruses.

~~~
wizzwizz4
Doesn't mean they were found not to.

------
urda
It's not a mystery. China is for sure not telling the truth. Remember this is
a country with massive censorship issues and have even kicked out foreign
reporters.

I'd like to know what the downvotes are? Because everything here is factually
true.

