littlebird says:
Some info on PCR tests specifically related to cycle threshold (ct) values:
American Clinical Laboratory Association (ACLA) letter to state labs re reporting ct values:
https://www.acla.com/wp-content/uploads/2021/01/ACLA-APHL-Ct-Value-Letter.pdf
https://archive.is/5UuTf
some excerpts (the full letter is ~2 pgs, linked above)
“We are writing to voice our concerns about potentially inappropriate use of Ct values with COVID-19 testing and to provide further information regarding the more appropriate scientific interpretation of Ct values obtained by PCR- based nucleic acid amplification methods.”
“In an effort to aid in the prioritization of COVID-19 cases with higher viral loads and potentially higher transmissibility, some state departments of health in recent months have requested that clinical laboratories report Ct values along with SARS-CoV-2 qualitative RNA test results. However, current scientific evidence and federal health agency guidelines urge caution against the use of Ct values from qualitative tests to inform case investigation, patient management, or public health surveillance efforts.”
“As your state considers requirements for laboratory reporting of SARS-CoV-2 RNA PCR test results, we urge caution against the potential misuse of Ct values for case investigation, patient management, or public health surveillance efforts. As noted above, there is currently no scientific consensus to support the use of Ct values for these purposes.”
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the ACLA letter also states: “To date, all COVID-19 PCR tests that have received Emergency Use Authorization (EUA) from the U.S. Food and Drug Administration (FDA) are qualitative tests, meaning that they are authorized to report a positive or negative result only.1”
citation: 1 In Vitro Diagnostics EUAs (30 Dec. 2020), available at https://www.fda.gov/medical-devices/coronavirus-disease- 2019-covid-19-emergency-use-authorizations-medical-devices/vitro-diagnostics-euas
but this is incorrect, the FDA FAQ now says:
https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medical-devices/covid-19-test-uses-faqs-testing-sars-cov-2
https://archive.is/D1BbM
“Q: Can laboratories report Ct values for authorized molecular diagnostic COVID-19 tests? (New 12/10/20)
A: Yes. Laboratories performing molecular diagnostic COVID-19 tests for the qualitative detection of SARS-CoV-2 report test results as being positive or negative. Under the molecular diagnostic emergency use authorizations (EUAs), laboratories can also report cycle threshold (Ct) values for authorized molecular diagnostic COVID-19 tests they perform.”
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a look at the ACLA Board of Directors is interesting:
https://www.acla.com/about-us/board-of-directors/
one of the Board members is
Stephen H. Rusckowski
Chairman, President and CEO
Quest Diagnostics
Quest stock had a meaty uptick in 2020.
https://ir.questdiagnostics.com/press-releases/press-release-details/2021/Quest-Diagnostics-Reports-Fourth-Quarter-And-Full-Year-2020-Financial-Results-Establishes-Outlook-For-First-Half-Of-2021/default.aspx
Gotta wonder if these financial returns (and other similar Pharma stock gains) are having any influence on the “advice” to labs not to report ct values.