WHO recommends lower PCR cycle counts

posted 3 years ago by TooheyWasWrong 3 years ago by TooheyWasWrong +40 / -0

Today the WHO is recommending lower cycle counts for PCR tests. This will reduce the number of positive cases.

Vaccination and Joe Biden will be attributed to the change

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– KirbyMorph 6 points 3 years ago +6 / -0

https://www.who.int/news/item/20-01-2021-who-information-notice-for-ivd-users-2020-05

WHO guidance Diagnostic testing for SARS-CoV-2 states that careful interpretation of weak positive results is needed (1). The cycle threshold (Ct) needed to detect virus is inversely proportional to the patient’s viral load. Where test results do not correspond with the clinical presentation, a new specimen should be taken and retested using the same or different NAT technology.

WHO reminds IVD users that disease prevalence alters the predictive value of test results; as disease prevalence decreases, the risk of false positive increases (2). This means that the probability that a person who has a positive result (SARS-CoV-2 detected) is truly infected with SARS-CoV-2 decreases as prevalence decreases, irrespective of the claimed specificity.

Most PCR assays are indicated as an aid for diagnosis, therefore, health care providers must consider any result in combination with timing of sampling, specimen type, assay specifics, clinical observations, patient history, confirmed status of any contacts, and epidemiological information.

They are updating standards and telling people to stop using PCR as a test result and that more cycles = more false positives and to stop using it.

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– RightOfSask -2 points 3 years ago +2 / -4

This is not new. This is just a reminder of a report from last September, which states the same. They have a link to the report in the reminder.

https://www.who.int/publications/i/item/diagnostic-testing-for-sars-cov-2

"Careful interpretation of weak positive NAAT results is needed, as some of the assays have shown to produce false signals at high Ct values. When test results turn out to be invalid or questionable, the patient should be resampled and retested."

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