"The PCR test analyzes samples by amplifying viral RNA in cycles. Most tests, like the Broad Institute test used by MIT, use a 40-cycle protocol. If the virus isn’t detected within 40 amplification cycles, the test result is negative. If viral RNA is detected in 40 cycles or less, the PCR machine stops running, and the test is positive. Because you received a positive result, we know that the test detected the virus in your sample by the time it reached its 40-cycle limit."
https://medical.mit.edu/covid-19-updates/2020/11/was-my-pcr-test-result-false-positive
"Dr. Anthony Fauci talking about Covid-19 PCR test cycle threshold of 35 or more"
"In December, his office issued an order to all state labs processing COVID PCR tests. They must now report “the number of cycles” they deploy in every test they perform. [1] [1a]
Roughly speaking, a cycle is a quantum leap which increases the sensitivity of the test. As readily asserted by Anthony Fauci, any test using more than 35 cycles is meaningless. [2] [2a]
—Not only meaningless, but laden with false-positive results. The patient is falsely claimed to be “infected.”
However, the FDA and the CDC, since the launch of the COVID PCR test, have been recommending using 40 cycles; and therefore labs have been following this advice. "
https://www.richardcyoung.com/covid-19/covid-pcr-tests-running-more-than-35-cycles-meaningless/