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2020-

2020-12-05 e
THE COVID-CON V - Essentially, Cycle Threshold (CT) value for PCR test over 32 yields false positives.
"Researchers observed a significant relationship between Ct value and culture positivity rate. Samples with Ct values of 13 to 17 all led to positive culture. Culture positivity rate then decreased progressively inversely proportional with Ct values, to reach 12% at a 33 Ct value. No culture was obtained from samples with Ct value of > 34."

Strong Inverse Correlation Between SARS-CoV-2 Infectivity and Cycle Threshold Value

Correlation between successful isolation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in cell culture and cycle threshold (Ct) value of quantitative reverse transcription polymerase chain reaction (RT-PCR) targeting E gene suggests that patients with coronavirus disease 2019 (COVID-19) with Ct above 33 to 34 are not contagious and can be discharged from hospital care or strict confinement, according to a brief report published in the European Journal of Clinical Microbiology & Infectious Diseases.

Previous research has observed that SARS-CoV-2 was detected by PCR up to 20 days after onset of symptoms; however, the virus could not be isolated after day 8 in spite of ongoing high viral loads of approximately 105 RNA copies/mL of sample. This highlights that isolation of patients with COVID-19 should be isolated after diagnosis. But due to the prolonged shedding of RNA in respiratory samples, when can a clinician consider a patient with COVID-19 as no longer contagious? (read more)

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