PCR is prone to contamination by very small amount of viral particles.
Hypothesis: we usually don't notice contamination, especially when it is happening *before* putting the probes into the PCR apparatus. This may even mimick a super spreader event.
Thread with examples
⬇️
NFL
France:
Contamination of a reagent. Not discovered by the laboratory, but by the local health authority which was skeptical about the sudden increase in cases.
amp.ouest-france.fr/grand-est/meur…
Germany:
Swab of a child was positive, because it was "highly contaminated by the biomaterial of a previous patient in the same practice"
ndr.de/nachrichten/me…
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Boston:
300 false positives
Reason not stated in this article, contamination possible
bnnbloomberg.ca/dna-firm-with-…
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Cyprus:
27 out of 30 positives were false positives due to contamination. Again, not recognized by the laboratory, but by local health officials that did a retest.
cyprus-mail.com/2020/08/26/cor…
🧵⬆️⬇️
NYS, Ulster county and Long Island:
>100 false positives "as a result of a specimen contamination issue".
Remember, in most cases, nobody questions a positive result, so these events could easily be interpreted as superspreading event.
therivernewsroom.com/false-positive…
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Quebec:
"dozens" of positive COVID-19 tests under review after "contamination issue
saultonline.com/2020/08/quebec…
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Arizona:
Early case in march, when the laboratories still had time to think twice:
"a specimen falsely tested positive at the state lab because during the extraction process some of a positive specimen contaminated another area on the test plate."
abc15.com/news/region-ph…
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Madagascar Pasteur Institute:
63 false +, not recognized. "A sample could contaminate an entire series. A. Spiegel, director of the Institut Pasteur: contamination could have affected the entire chain, from taking samples to arrival at the institute."
google.com/amp/s/amp.rfi.…
🧵↕️
Sestao, Spain:
29 false positives due to "a technical error in a batch of tests, these were contaminated , which caused a series of false positives. " - could something like this be falsely classified as a superspreading event?
eitb.eus/es/noticias/so…
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UArizona:
11 false+ athletes.
Always keep in mind: normal people won´t get a retest. That we find so much false + in athletes and celebrities is not by chance.
"and when moving the samples in an automated fashion, there was some *contamination*"
azfamily.com/news/continuin…
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27 false positives "due to a contamination". One of them a doctor who insited on a re-test; otherwise unnoticed.
eldiariomontanes.es/cantabria/micr…
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USA
Alex Dickerson, another athlete false +. Remember, ordinary people go to quarantine without a retest...
“It’s impossible to say if the sample was contaminated at some point, whether that was during collection, during transit, at the lab itself”
knbr.com/2020/09/13/ale…
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Taos County
"Spike in new cases" - 10 false positives
"samples were on a single testing plate with 384 specimens."
taosnews.com/coronavirus/up…
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Baltimore:
False-positive tests "in the dozens". Again, not recognized by the lab, but by a nursing home provider that was suspicious about the high rate of positives and made re-tests. Again, this could have been taken for a super spreading event.
wbaltv.com/article/corona…
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Texas:
Series of false-+ in nursing homes, number unknown. Authorities closed the lab, that " didn’t follow procedures to prevent contamination of patient samples, such as keeping patient specimens covered and ensuring workers wore fresh lab coats"
google.com/amp/s/www.govt…
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Germany, Niedersachsen:
Series of false positives (>10) due to "a contaminated device". Several schools closed, than reopened. Luckily, not interpreted as a superspreader event.
google.com/amp/s/hildeshe…
ndz.de/lokales/bad-mu…
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Michigan, Allendale:
30 students sent to quarantine, due to one false positive, who was re-tested "and they realized that there may have been an issue with some cross contamination"
fox17online.com/news/31-studen…
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Atlanta, Football:
Error cluster, probably contamination. Again in athletes. Remember, normal people won't get a retest.
"4/135 tested positive for CoV from our 3rd test in 4 days as part of our protocol .. a human error Friday caused the error"
11alive.com/article/sports…
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NFL, Houston Texans:
Next "batch of false positives "... The situation, "though not nearly as widespread, was similar to an outbreak last month." Remember, it was lab contamination last month.
sports.yahoo.com/houston-texans…
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German cruise ship:
12/150 tests false positive ... "8% false-positive rate on the ship is a puzzle", according to experts.
No, it´s not a puzzle. It´s probably contamination. Have a look in this thread ☝️
n-tv.de/panorama/Erneu…
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Italy, Forli:
Another cluster error in a soccer team, 5 tested positive, all negative in control swab.
What a coincidence, that this happens in athletes and celebrities all the time, but never in normal people!
forlitoday.it/sport/coronavi…
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Brazil, São Paulo:
71 false positives, among them 27 athletes -> retest
"2 batches of imported reagents ( primers ) with operating instability were identified , probably responsible for the divergence.”
poder360.com.br/coronavirus/pr…
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