Here it is again...Minnesota's state lab admits less than half its PCR "positives" in the past 3 months were under 30 Ct.Bart wrote: ↑Fri Sep 11, 2020 12:47 pmGood question. I don't have a good answer. After talking with someone who does RT-qPCR alot, we both just kind of shrugged our shoulders. Perhaps with such high cycle counts they can be certain a false is a false? Err on the side of false positives rather than false negatives? The guidelines show the tests have Level of detection down to 10 virus particle/microliter titers but that is with cycles in the 34 - 36 range depending on machine and extraction kit used. Perhaps this has something to do with it? Sorry I do not have a better answer.youthathletics wrote: ↑Fri Sep 11, 2020 8:31 amHelp us out here. if Ct value is inverse to a positive, then why is anything greater than 33-34 being used to indicate a positive/contagious person by the CDC/Labs?Bart wrote: ↑Fri Sep 11, 2020 7:43 amVery simple, quick explanation of Cycle threshold, if anyone is interested: https://www.wvdl.wisc.edu/wp-content/up ... alues1.pdfyouthathletics wrote: ↑Fri Sep 11, 2020 7:30 am Interesting conversation, seems the CDC is using Ct values greater than 30 to define positives. https://twitter.com/EthicalSkeptic/stat ... 64801?s=20
THis study implies what the poster on Twitter is saying...
https://www.infectiousdiseaseadvisor.co ... ischarged/
Correlation between successful isolation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in cell culture and cycle threshold (Ct) value of quantitative reverse transcription polymerase chain reaction (RT-PCR) targeting E gene suggests that patients with coronavirus disease 2019 (COVID-19) with Ct above 33 to 34 are not contagious and can be discharged from hospital care or strict confinement, according to a brief report published in the European Journal of Clinical Microbiology & Infectious Diseases
This stuff is certainly interesting. Maybe they (labs and CDC, etc) are using this high Ct as a higher standard, which provides them wiggle room to argue they wanted a much higher safety factor? Unfortunately the article cited, implies differently, which appears to skew the numbers we are seeing in favor of the virus still being highly active..and yet, states are relaxing more and more.
There is certainly a disconnect between what we hear and read, vs. what we are seeing.
Based on this data, researchers deduced that patients with Ct values > 34 do not excrete infectious viral particles and thus may be discharged.
On another interesting nerd note. Here is a preprint of a paper that looks at Ab binding and how to design antibody "cocktails" to take into account "escape" mutations to occur that will effect the binding of a single antibody. https://www.biorxiv.org/content/10.1101 ... 0.292078v1
Seems the Ct is all over the place, which really just throws all the resultant testing data we see into one big bucket of uncertainty.