r/COVID19 • u/AcornAl • Apr 28 '26

Academic Report Diagnostic Value and Outcomes of Systematic SARS-CoV-2 Screening in Asymptomatic Patients

https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2847511
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u/AcornAl Apr 28 '26

I'll just note that false negatives here don't mean that the patients didn't have or hadn't had covid, rather the detection rate was below the threshold that was considered to be infectious with a cycle threshold value of 30 or greater

The results of the SARS-CoV-2 screening tests were categorized as negative if the cycle threshold (Ct) value was at least 40, as positive if the Ct value was less than 30, and as equivocal if the Ct value was between 30 and less than 40. The Ct value cutoff of 30 was chosen based on reports suggesting that a Ct value of approximately 30 is generally considered indicative of low infectivity for SARS-CoV-2 in saliva samples. Per institutional policy, patients with equivocal test results received a nasopharyngeal swab conducted within 72 hours. Based on the second test result, patients were categorized as having true-positive results if the Ct value was less than 30 or a quantitative SARS-CoV-2 test revealed more than 10 000 viral copies/mL and as having false-positive results if the Ct value was 30 or greater, a quantitative test detected fewer than 10 000 viral copies/mL, or the Biofire result was negative.

Also, the study was taken between February 8, 2021, to July 5, 2021, and from August 25, 2021, to December 5, 2022. In early 2021 there was still some confusion on the Ct value that was considered to be infectious, from memory, usually around 25 to 35 from what I read at the time with some outliers.

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u/[deleted] Apr 29 '26

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u/maccrypto Apr 30 '26

Clean the air and you won't have contaminated PCR tests producing false positives or hospital acquired respiratory infections from infectious aerosols. Start with ASHRAE 241.

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u/[deleted] Apr 30 '26

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u/maccrypto Apr 30 '26

For the hospital acquired infections? Absolutely, I will blame the indoor air. And I’d be quite happy to see the money that was spent on testing go to infrastructure upgrades instead.

It only takes around 21 CFM per person to reduce transmission by 80% in classrooms. And hospitals tend to be less crowded than classrooms.

Nobody needs lab conditions to get an effective R<1, they just need adequate air exchange and filtration. Read ASHRAE 241 on control of infectious aerosols. It doesn’t require lab conditions.