Sunbelt governors have bucked the lockdown overlords for the most part. Florida Governor Ron DeSantis has been a leader in this fight, declaring that the state will never lockdown again. Now Florida has picked up the correct thread on COVID-19 testing. On December 3, in a joint statement, DeSantis and Florida Surgeon General Scott A. Rivkees announced that labs must report the cycle threshold (Ct) and reference ranges on every single test.
This is important because the higher the Ct, the less likely a person who tests positive will actually become ill or be contagious. In August, a New York Times feature article reported that up to 90% of tests taken in New York, Nevada, and Massachusetts were essentially false positives. The Ct, or number of times a sample is magnified, was so high it could pick up very low levels of the virus.
According to experts interviewed for that article, the correct cutoff to call a test positive was likely a Ct between 30 and 35. The noted labs in the United States were going as high as 37 to 40. This rate would find a significantly higher number of positive “cases.” Because this number is the one breathlessly reported by the media and used as justification for lockdowns and other draconian policies, the number of true positives matters.
Because the Times’ analysis showed such a high number of tests above a cycle threshold that the experts agreed indicated infectious disease, it’s clear that resources are being misdirected. In an environment in which local public health leaders are trying to forecast health system needs and provide contact tracing, it is imperative they have accurate data.
As an example, on Sunday, 1,808 positive tests were reported in Georgia. If the number of tests that actually indicate contagious illness was closer to 180-200, this would paint a very different picture in the state. Contact tracers could effectively notify close contacts. It would also enhance the health system’s ability to monitor available hospital beds.
A recent study also indicated that for public policy, a Ct between 30 and 35 is probably the right number, while taking into account the patient’s condition. Evaluating the patient’s outward symptoms and the Ct is probably a good approach for individual care and directing public health resources.
Michael Mina, a physician and an epidemiologist at Harvard University’s T.H. Chan School of Public Health, echoed this sentiment in an interview with Science Magazine:
But Mina and others say the recent findings also suggest that a patient who has undergone multiple tests with high CT values is likely at the tail end of their infection and need not isolate themselves. He adds that contact tracers should triage their efforts based on CT values. “If 100 files land on my desk [as a contact tracer], I will prioritize the highest viral loads first, because they are the most infectious,” Mina says.
The New York Times analysis was retrospective, and studies were conducted in the laboratory setting. Now Florida will collect data in a real-world setting. The most current CDC guidelines on the use of PCR tests under an Emergency Use Authorization from the FDA still require a Ct of 40. In July, Dr. Fauci said there was a consensus view that a Ct < 35 indicated COVID-19 infections:
Joining the hosts of This Week in Virology in July, Fauci directly responded to a question about COVID-19 testing, specifically how patients with positive tests might determine whether or not they are actually infectious and need to quarantine.“
What is now sort of evolving into a bit of a standard,” Fauci said, is that “if you get a cycle threshold of 35 or more … the chances of it being replication-[competent] are minuscule.”
“It’s very frustrating for the patients as well as for the physicians,” he continued, when “somebody comes in, and they repeat their PCR, and it’s like [a] 37 cycle threshold, but you almost never can culture virus from a 37 threshold cycle.”
So, I think if somebody does come in with 37, 38, even 36, you got to say, you know, it’s just dead nucleotides, period.”
A legitimate question is why the CDC guidance on EUA tests has not changed to reflect this consensus and other studies to date. Every state should follow Florida’s lead and start collecting this information. It will provide a much more accurate picture of the pandemic and allow for better resource utilization.