A thread on PCR testing and cycle thresholds. More details are available in the linked article:

1/11 https://rationalground.com/why-mass-pcr-testing-of-the-healthy-and-asymptomatic-is-currently-counter-productive/

The problem is that current PCR tests provide evidence of the presence of viral RNA but no information about whether the individual is infectious.

In a French study on the duration of infectiousness, scientists cultured samples from PCR tests and found...

2/11

... that the culture positivity rate (a measure of the viability of the virus) decreased with the number of cycles that it took to detect that virus. No culture was obtained from samples that required more than 34 cycles.

3/11

A recent New York Times article presented evidence that specimens detected in 27 to 34 cycles rarely show any live virus, and specimens detected above 34 cycles never show any live virus.

4/11

The FDA’s Instructions for Use for the CDC 2019-Novel Coronavirus (2019-nCoV) Real-Time RT-PCR Diagnostic Panel currently recommends a threshold of 40 cycles for a specimen to be considered positive, well above the recommendations of the studies cited above.

5/11

The decision to equate a positive PCR test with a “case” in the COVID-19 pandemic is not aligned with recommendations from the test manufacturers or with definitions of cases for other viruses.

6/11

For SARS-CoV-1, the CDC and WHO recommended testing only patients “with a high index of suspicion for having SARS-CoV-1 disease” and re-testing positive specimens in a reference laboratory.

7/11

When a PCR specimen indicated infection, the recommendation was to test a second specimen.

The new recommendation to only test symptomatic or exposed people is a good start to address the hysteria caused by rising case numbers, particularly in young people.

8/11

However, an additional change is needed: the FDA recommendation for 40 cycles of amplification in PCR testing is far too sensitive and is leading to alarm about high numbers of “cases” in asymptomatic people

9/11

The FDA should update their guidance to recommend no more than 34 cycles, require labs to communicate the number of cycles required to detect the virus for each positive test, and...

10/11

... require labs to disclose the cycle threshold for all previous COVID tests to clean up the inflated statistics (cases, hospitalizations, and deaths) associated with test results that exceeded 34 cycles.

11/11