The ELISA used by the authors has a stated specificity of 99.3% and the authors tested 519 "true negative" blood samples collected from 2016 to 2019 from healthy adults and suspected hanta virus patients and observed 3 false positives (0.6%) matching this specificity. 3/10
-
Show this thread
-
The authors tested 1912 blood samples collected between Dec 13 and Dec 16 2019 and observed 39 positives (2.0%). A Fisher's Exact Test comparing 3/519 to 39/1912 is narrowly significant with p = 0.02. 4/10
1 reply 12 retweets 137 likesShow this thread -
However, there is ample reason to expect that individuals recently recovered from seasonal coronavirus infection will have more cross-reactivity to SARS-CoV-2 than random healthy adults. In fact this can be seen in this paper by Freeman et al (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7239067/ …). 5/10
7 replies 24 retweets 231 likesShow this thread -
Here, ELISA titers are higher in individuals who were recently infected with seasonal coronavirus compared to random healthy adults. This is particularly the case in related betacoronaviruses OC43 and HKU1. 6/10pic.twitter.com/ljh7UC8qPZ
1 reply 13 retweets 140 likesShow this thread -
Additionally, we know that seasonal coronaviruses circulate at higher frequencies in the winter. We can see this in
@seattleflustudy data where there is significant seasonal coronavirus circulation in Dec 2019. 7/10pic.twitter.com/VrvdtRKllp
5 replies 16 retweets 146 likesShow this thread -
It seems highly likely to me that the 39 "positives" from Dec 13 to Dec 16 reported by Basavaraju et al are due to cross-reactivity from recent seasonal coronavirus infection. It would just take a slight decrease of assay specificity to ~98% to explain this outcome. 8/10
8 replies 56 retweets 275 likesShow this thread -
The authors highlight the study's limitation due to "potential cross reactivity with human common coronavirus infection" in the paper's discussion, but it unfortunately didn't make it into the
@WSJ story (https://www.wsj.com/articles/covid-19-likely-in-u-s-in-mid-december-2019-cdc-scientists-report-11606782449 …). 9/105 replies 55 retweets 333 likesShow this thread -
The other angle to consider is that if we're supposed to believe that 2.0% of random blood donors in Dec 2019 are COVID+ this would translate to millions of infections in the population at large, in which case we would have noticed due to people dying in large numbers. 10/10
36 replies 78 retweets 625 likesShow this thread -
Trevor Bedford Retweeted Trevor Bedford
Follow up #1: Also, a reminder that we at the
@seattleflustudy PCR tested 3600 samples from individuals with acute respiratory illness collected in January 2020 from Seattle and found zero positives for COVID-19. This is a much more specific assay.https://twitter.com/trvrb/status/1249414295042965504 …Trevor Bedford added,
Trevor BedfordVerified account @trvrbWe tested 3600 samples collected in Jan 2020 for COVID-19 status and found zero positives. We tested 3308 samples collected in Feb 2020 and found a first positive on Feb 21 with a total of 10 samples testing positive in Feb. 5/18 pic.twitter.com/Jcx0qzdfx8Show this thread8 replies 65 retweets 341 likesShow this thread -
Follow up #2: This doesn't mean that COVID-19 was completely absent from the US in January 2020, just that prevalence at that time was exceptionally low. Finding 0/3600 COVID+ acute respiratory specimens doesn't square with theoretical 2% ELISA positivity in Dec.
22 replies 41 retweets 284 likesShow this thread
Could we test this theory by re running the study on blood samples from, say, January 2018?
-
-
Replying to @GidMK
Yeah. I'd expect 1-2% ELISA positives from blood samples from Dec 2018 and ~0.5% ELISA positives from blood samples from June 2019.
5 replies 0 retweets 16 likes -
- Show replies
New conversation -
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.
