July 16, 2020
4:06 Q: Can we use a cutoff of viral loads determined by PCR to say "This patient is no longer infectious, can go home, can go to a nursing facility. Because right now the physicians are really having a hard time with that."
4:20 Fauci Answer: Again, a good question. What is now sort of evolving into a bit of a standard, that if you get a cycle threshold of 35 or more the chances of it being replication competent are miniscule. We have patients, it's very frustrating for the patients and the physicians...Somebody comes in and they repeat their PCR and it's like 37 cycle threshold. You can almost can never culture virus from a 37 threshold cycle. So I think if somebody comes in with a 37, 38, even 36, you gotta say it's just dead nucleotides period.
4:12 Question: Because, as you know, we can't easily culture infectious virus. You don't have a BSL 3 lab everywhere.
5:30 Fauci Answer: When someone comes in and it's positive they don't give them the threshold until you go back and ask for it.
Some discussion about the labs in Kansas:
Kansas labs set cycle thresholds too high, detect non-contagious virus
Some really heady reading for you:
SARS-CoV2 Testing: The Limit of Detection Matters
if you’re into twitter:
Dr. David Samadi, MD
@drdavidsamadi
PCR tests are unreliable due to the amplification threshold. Anything over 17 cycles is worthless. In the USA, we use 35 cycles. The WHO recommends 40 to 45 cycles. Totally worthless. At that many amplifications you are just picking up the presence of any virus. Useless.
https://twitter.com/drdavidsamadi/status/1340340552965959681