CT value is not a reliable indicator. Earlier labs used to report CT value by default but now they do not - but one can ask for the CT value. https://www.icmr.gov.in/pdf/covid/techdoc/Advisory_on_correlation_of_COVID_severity_with_Ct_values.pdf
On Fri, Jan 15, 2021 at 11:18 AM Nikhil VJ <nikhil...@gmail.com> wrote: > Hi All, > > I wanted to know if the Indian government or related agencies have set any > standard limit in a crucial setting in the Covid tests called "Cycle > Threshold". > > Are the folks collecting stats on covid cases - having any data on cycle > values for those cases? > > Have you or someone you know been diagnosed as a Covid-19 case? What was > the cycle value in your test result? Does the lab that did the test share > this data? > > Sharing an article and some excerpts from it: > > > https://www.msn.com/en-us/health/medical/experts-us-covid-19-positivity-rate-high-due-to-too-sensitive-tests/ar-BB18wE8B > Experts: US COVID-19 positivity rate high due to 'too sensitive' tests > > "With a cutoff of 35, about half of those tests would no longer qualify as > positive. About 70 percent would no longer be judged positive if the cycles > were limited to 30. > In Massachusetts, from 85 to 90 percent of people who tested positive in > July with a cycle threshold of 40 would have been considered negative if > the threshold were 30 cycles, Mina said. " > "The Food and Drug Administration said that it does not specify the cycle > threshold ranges used to determine who is positive and 'commercial > manufacturers and laboratories set their own.'" > "The CDC said its own calculations suggest its extremely hard to detect a > live virus in a sample above a threshold of 33 cycles. " > > > This was one - there's many more if I search for "RT-PCR test cycle > threshold value covid" on duckduckgo. (tip: google search is broken when it > comes to anything controversial. Proverbial case of overprotective mother > suffocating the child in the quest to protect it. Take the same query and > run it in Bing, Duckduckgo etc also.) > > Looking into this I'm seeing an analogy with vectorizing raster satellite > imagery : Your software can easily fill the whole thing up with false > positives, or can produce no result at all. Lot of fine tuning is required > to get the "perfect setting" that minimizes the false positives and false > negatives, and you often never reach a perfect setting that didn't have any > mistakes. It's not a hard yes/no thing. You invariably need manual > intervention (and even with AI interventions we're seeing problems), and it > frustrates the hell out of people who assumed this technology thing is a > silver bullet. > > Inviting people with better knowledge on this topic to correct me: My > understanding is that there is an exponential (maybe doubling, maybe some > other factor) change from one Ct value to the other. To go from 33 to 40, > would be.. well, non-trivial. > > So one set of data needed is : What are the Ct limits being used in > current testing? Is there a single value standardized by the government? If > there is variation, then who decides? > > Another set of data that can be just as useful : Have these Ct limits been > changed since the pandemic began almost a year ago? How have they changed, > and is there any co-relation between that and the Covid+ case counts? Is it > possible to "explode" / "reign in" a pandemic by merely altering this > setting without any ground level realities changing? If yes, then why is > talk about it missing from the mainstream discourse? > > > -- > Cheers, > Nikhil VJ > https://nikhilvj.co.in > > -- > Datameet is a community of Data Science enthusiasts in India. Know more > about us by visiting http://datameet.org > --- > You received this message because you are subscribed to the Google Groups > "datameet" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to datameet+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/datameet/CAH7jeuM%2BFh7nsNGzaF5PkTxR-VUA%2B9vce7%3DwCRWcxiVnKYsKQQ%40mail.gmail.com > <https://groups.google.com/d/msgid/datameet/CAH7jeuM%2BFh7nsNGzaF5PkTxR-VUA%2B9vce7%3DwCRWcxiVnKYsKQQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- Datameet is a community of Data Science enthusiasts in India. Know more about us by visiting http://datameet.org --- You received this message because you are subscribed to the Google Groups "datameet" group. To unsubscribe from this group and stop receiving emails from it, send an email to datameet+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/datameet/CA%2BDCqDgqA-RfnxT0emvNF8U6eYfQGc8oPAewKO1asGBa92DN_w%40mail.gmail.com.
