Cycle threshold values of positive PCR tests for Covid-19

Misty made this Freedom of Information request to Public Health England

Automatic anti-spam measures are in place for this older request. Please let us know if a further response is expected or if you are having trouble responding.

The request was refused by Public Health England.

Dear Public Health England,

I have a number of questions related to using the PCR test to diagnose Covid-19:

1) Can you tell me the distribution of cycle thresholds used to provide a positive PCR test? In other words, what percentage of positive tests came at what cycle threshold value?

2) Have you undertaken any viral culture to cross reference with cycle threshold values? If so, what are the results? Additionally, if you have any information about the proportion of culturable samples by cycle threshold can you please provide those.

3) Can you please the approximate false positive and false negative rates for your PCR test? Does this vary with cycle threshold?

Yours faithfully,

Misty

FOI, Public Health England

Dear Misty

Thank you for your email.

In order to process your request, please provide us with your full name. As soon as this is provided we will process your request. Under Section 16 of the FOI Act, public authorities have a duty to provide advice and assistance. Accordingly, please visit the Information Commissioner’s Office (ICO)’s website on the following link which provides guidance it’s definition on what constitutes to a real name: https://ico.org.uk/media/for-organisatio...

Kind regards

FOI Team
Public Accountability Unit
Public Health England
[Public Health England request email]
Tel: 020 8327 6920
www.gov.uk/phe Follow us on Twitter @PHE uk

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Dear FOI Team,

My full name is Chris Jones

Yours sincerely,

Chris Jones (AKA Misty)

FOI, Public Health England

Dear Chris Jones

We acknowledge receipt of your email and request for information, which will be treated as a request for information under statutory access legislation.

Please note that requests under the Freedom of Information Act and the Environmental Information Regulations (EIRs) will receive a response within 20 working days from the day following the date of receipt of your request.

If the request is for your personal data, your request has been handled as a data subject access request (SAR) under Article 15 of the General Data Protection Regulation (GDPR), then we will respond within one month of the receipt of the request.

Public Health England (PHE) is responsible for providing guidance and advice to government and front-line services for all aspects of public health. It is a designated Category 1 responder organisation under the Civil Contingency Act and this specifically includes the COVID-19 response, providing clinical expertise and wider public health advice and guidance across national and local government, the NHS and third sector. As such, you may experience delays when making statutory information access requests during the pandemic.

We will aim to address all requests promptly and within the required response timeframes. However when we are unable to meet the response timeframe we will keep requesters updated on a revised expected timescale for a response to their request. The Information Commissioner recognises this position in its recent guidance, see link: https://ico.org.uk/global/data-protectio....

FOI Team
Public Accountability Unit
Public Health England
[Public Health England request email]
www.gov.uk/phe Follow us on Twitter @PHE uk

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FOI, Public Health England

1 Attachment

  • Attachment

    1845 FOI Information requested on the usage of PCR testing to diagnose Covid 19.pdf

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Dear Chris Jones

Please find attached Public Health England's response to your request.

FOI Team
Public Accountability Unit
Public Health England
[Public Health England request email]
www.gov.uk/phe Follow us on Twitter @PHE uk

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Dear FOI,

Thank you for your response, although I'm a little frustrated in the response to the first question where you state "PHE can confirm it does not hold information in the way suggested by your request."

This suggests you have some information! Can you share any data you have that might help me understand the CT values that have been used please.

Yours sincerely,

Misty

FOI, Public Health England

Dear Chris Jones

As advised in our response, PHE does not hold the information you have requested. This is because Cycle thresholds (Ct) used to determine a positive COVID-19 PCR test will differ depending on the assay used. Further data is available from the commercial manufacturer of the assay and is subject to local validation by the laboratory using the test and before using it for diagnostic purposes.

Under section 16 of the Act, public authorities have a duty to provide advice and assistance. You may wish to review the link provided in your response which provides details about interpreting CT values: https://assets.publishing.service.gov.uk...

Additionally, this page holds assessments of laboratory tests and assays which you may find useful:
https://www.gov.uk/government/collection...

Kind Regards
FOI Team
Public Accountability Unit
Public Health England
[Public Health England request email]
www.gov.uk/phe Follow us on Twitter @PHE uk

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