Unspecific, Prone to False Positives, Uncalled For
PCR tests have a precision in amplifying cycles to find RNAs they are looking for, however it is not suitable for infection diagnostics because it will find most or all the RNA’s among the coronaviruses they are looking for after so many cycles. Ten cycles is enough to tell there is probably a viral load of infection. However, most labs in the US do 30-40 cycles, which often causes up to 90% false positives. The test was never meant for infection diagnostics because it cannot tell between live and dead viruses, nor distinguish the shared RNAs of the hundreds of coronaviruses, four of which affect humans like the common cold.
Correlation Between 3,790 Quantitative PCR–Positives Samples and Positive Cell Cultures →
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The outbreak of the coronavirus disease 2019 (COVID-19) pandemic due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was declared a pandemic on 12 March 2020 by the World Health Organization. A major issue related to the outbreak has been to correlate viral RNA load obtained after reverse-transcription polymerase chain reaction (RT-PCR) and expressed as the cycle threshold (Ct) with contagiousness and therefore duration of eviction from contacts and discharge from specialized infectious disease wards.
Several recent publications, based on more than 100 studies, have attempted to propose a cutoff Ct value and duration of eviction.
…in an article published in Clinical Infectious Diseases, Bullard et al reported that patients could not be contagious with Ct >25 as the virus is not detected in culture above this value.
…It can be observed that at Ct = 25, up to 70% of patients remain positive in culture and that at Ct = 30 this value drops to 20%. At Ct = 35, the value we used to report a positive result for PCR, <3% of cultures are positive."
Several recent publications, based on more than 100 studies, have attempted to propose a cutoff Ct value and duration of eviction.
…in an article published in Clinical Infectious Diseases, Bullard et al reported that patients could not be contagious with Ct >25 as the virus is not detected in culture above this value.
…It can be observed that at Ct = 25, up to 70% of patients remain positive in culture and that at Ct = 30 this value drops to 20%. At Ct = 35, the value we used to report a positive result for PCR, <3% of cultures are positive."
Oxford Academic: Clinical Infectious Diseases
EDITOR NOTE: This study confirms a meta-analysis of more than 100 studies indicating that at a Ct (Cycle threshold) of 35 or over the PCR test yields 97% false positives.
Performance of SARS-CoV-2 RT-PCR test as a tool for detecting SARS-CoV-2 infection in the population →
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We analysed real-world data from a large laboratory in the city of Münster (population 313,000), Germany… This laboratory performed about 80% of all SARS-CoV-2 RT-PCR tests in the Münster region during this time (162,457 tested individuals)…
In light of our findings that more than half of individuals with positive PCR test results are unlikely to have been infectious, RT-PCR test positivity should not be taken as an accurate measure of infectious SARS-CoV-2 incidence. Our results confirm the findings of others that the routine use of “positive” RT-PCR test results as the gold standard for assessing and controlling infectiousness fails to reflect the fact “that 50-75% of the time an individual is PCR positive, they are likely to be post-infectious“.
In light of our findings that more than half of individuals with positive PCR test results are unlikely to have been infectious, RT-PCR test positivity should not be taken as an accurate measure of infectious SARS-CoV-2 incidence. Our results confirm the findings of others that the routine use of “positive” RT-PCR test results as the gold standard for assessing and controlling infectiousness fails to reflect the fact “that 50-75% of the time an individual is PCR positive, they are likely to be post-infectious“.
Journal of Infection
Anthony Fauci on PCR →
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if you get a cycle threshold of 35 or more that the chances of it being replication competent are minuscule…you almost never can culture virus from a 37 threshold cycle. So I think if somebody comes in there with 37/38 even 36 you gotta say it’s just dead nucleotides period.”
Reddit
PCR TESTING blog →