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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
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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.https://amp.ouest-france.fr/grand-est/meurthe-et-moselle/coronavirus-apres-une-serie-de-tests-errones-des-chiffres-a-nouveau-rassurants-en-meurthe-et-moselle-6888935 …
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Germany: Swab of a child was positive, because it was "highly contaminated by the biomaterial of a previous patient in the same practice"https://www.ndr.de/nachrichten/mecklenburg-vorpommern/Graal-Mueritz-Corona-Test-war-fehlerhaft-Schule-oeffnet-wieder,coronavirus2884.html …
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Boston:
300 false positives
Reason not stated in this article, contamination possiblehttps://www.bnnbloomberg.ca/dna-firm-with-history-of-errors-botched-nursing-home-covid-tests-1.1489499 …Näytä tämä ketju -
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.https://cyprus-mail.com/2020/08/26/coronavirus-clinic-temporarily-suspended-from-testing-after-airport-group-false-positives-update-2/ …Näytä tämä ketju -
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.https://therivernewsroom.com/false-positives-skew-test-results-in-dutchess-ulster-counties/ …Näytä tämä ketju
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Quebec:
"dozens" of positive COVID-19 tests under review after "contamination issue
https://saultonline.com/2020/08/quebec-reviewing-dozens-of-positive-covid-19-tests-after-contamination-issue/ …Näytä tämä ketju
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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."https://www.abc15.com/news/region-phoenix-metro/central-phoenix/positive-covid-19-test-at-az-state-lab-now-negative-after-cross-contamination …Näytä tämä ketju
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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."https://www.google.com/amp/s/amp.rfi.fr/en/africa/20200516-pasteur-institute-in-madagascar-admits-errors-in-its-covid-19-analysis …Näytä tämä ketju
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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?https://www.eitb.eus/es/noticias/sociedad/detalle/7450673/covid19-casos-brotes-coronavirus-euskadi-navarra-26-agosto-2020/ …Näytä tämä ketju
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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*"https://www.azfamily.com/news/continuing_coverage/coronavirus_coverage/uarizona-president-explains-false-positive-covid-19-tests/article_5cbc59f2-f2ca-11ea-a824-c3b0a872ab5e.html …Näytä tämä ketju
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27 false positives "due to a contamination". One of them a doctor who insited on a re-test; otherwise unnoticed.https://www.eldiariomontanes.es/cantabria/microbiologia-eleva-positivos-20200820214433-nt.html …Näytä tämä ketju
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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”https://www.knbr.com/2020/09/13/alex-dickersons-weekend-from-hell-likely-false-positive-completely-false-report/ …Näytä tämä ketju
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Taos County
"Spike in new cases" - 10 false positives
"samples were on a single testing plate with 384 specimens."https://www.taosnews.com/coronavirus/updates/testing-mixup-results-in-false-positives-for-taos-county/article_dbeb94b4-f648-5799-9760-2960be716d33.html …Näytä tämä ketju
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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.https://www.wbaltv.com/article/coronavirus-false-positive-results-at-nursing-homes/34061283 …Näytä tämä ketju
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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"https://www.google.com/amp/s/www.govtech.com/em/safety/-Texas-Lab-Problems-Threaten-Coronavirus-Patient-Safety-Feds-say.html%3fAMP …Näytä tämä ketju
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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.
https://www.google.com/amp/s/hildesheimer-presse.de/2020/09/04/corona-laborfehler-fuehrt-zu-falschen-testergebnissen-10-personen-sind-nicht-infektioes-keine-positiven-coronafaelle-an-schulen-und-kita/amp/ …
https://www.ndz.de/lokales/bad-muender_artikel,-kontamination-falsche-positive-coronabefunde-_arid,2639890.html …Näytä tämä ketju
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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"https://www.fox17online.com/news/31-students-back-in-class-after-cross-contamination-mistake-found …Näytä tämä ketju
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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"https://www.11alive.com/article/sports/ncaa/ncaaf/georgia-state-football-covid-false-positives/85-c3228de1-93bc-446d-80b1-61f5839e5e9f …Näytä tämä ketju
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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.
https://sports.yahoo.com/houston-texans-false-positive-coronavirus-covid19-tests-pittsburgh-steelers-235910984.html …Näytä tämä ketju
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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
https://www.n-tv.de/panorama/Erneute-Tests-auf-Mein-Schiff-6-negativ-article22066512.html …Näytä tämä ketju -
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!https://www.forlitoday.it/sport/coronavirus-falsi-positivi-tamponi-negativi-rientra-la-paura-in-casa-forli-calcio.html …Näytä tämä ketju
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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.”https://www.poder360.com.br/coronavirus/procon-sp-notifica-albert-einstein-por-erro-em-testes-de-covid-19/ …Näytä tämä ketju
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Trinity county, USA
"Trinity county hospital cluster doesn't exist". Another cluster error involving 7 patients in a hospital. Contamination is difficult to differentiate from real clusters or super spreading events.
https://kymkemp.com/2020/10/08/trinity-county-covid-cluster-doesnt-exist-report-based-on-false-positives/ …Näytä tämä ketju
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Chennai, India
44/139 Test false positive," a reason could be carelessness in handling samples and contamination" and "Those with Covid positive report received mediclaim amount from insurers even in home isolation"https://timesofindia.indiatimes.com/city/chennai/chennai-lab-sealed-for-false-positive-results/articleshow/78630654.cms …Näytä tämä ketju
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NFL, Colts:
another cluster of 4 false positives. "What remains unclear is why the NFL has had so many false positives."
Is anyone keeping track of true/false positives for NFL? I didn't count but I have the feeling it's in the 10-40% FPR range?https://profootballtalk.nbcsports.com/2020/10/16/colts-say-all-four-tests-were-false-positives-game-vs-bengals-is-on/ …Näytä tämä ketju
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Tämä twiitti ei ole saatavilla.
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Bavaria:
Next series of false positives in two bavarian soccer clubs. Athletes are the only population with systematic double tests. PCR tends to fail in clusters - in the normal population, we would call these super spreading events.
https://www.br.de/nachrichten/sport/wirbel-um-falsch-positive-corona-tests-im-profifussball,SERMrnl …Näytä tämä ketju
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Madrid, Spain:
9 positives "at one go" - a super spreading event, or merely a contamination in the lab? Unless you are an athlete, you will never know, as you don´t get retested. This soccer Team did 4x retest on all positives, all came back negativehttps://www.lavanguardia.com/deportes/futbol/20201023/484236855190/alcorcon-coronavirus-positivos-sabadell-segunda-division.html …Näytä tämä ketju
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El Hiero, Spain:
When PCR fails, it fails in clumps. Super Spreading on the canary islands? No - "initial result of 60 positives for covid-19", but "it has been determined that the figure is 1 and that 59 were flawed tests."https://queeniesdailysnippets.wordpress.com/2020/10/15/59-false-positives-in-el-hierro/ …Näytä tämä ketju
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