Public Accountability Unit
T 020 8327 6920
133-155 Waterloo Road
London SE1 8UG
Our ref: 18/02/ay/2838
10 March 2021
Dear Chris Dodd, Re: 2838 - FOI Cycle threshold to run PCR Test before 20th July 2021
Thank you for your request received on 18 February 2021 addressed to Public
Health England (PHE). In accordance with Section 1(1)(a) of the Freedom of
Information Act 2000 (the Act), I can confirm that PHE does partly hold the
information you have specified.
At what cycle threshold was recomended to run a pcr test before the 20th of
PHE can confirm it does hold the information requested in relation to PCR tests used
within PHE laboratories. PHE has also assumed that your request was in relation to
cycle threshold before 20 July 2020 rather than 2021 as per your request.
Cycle threshold (Ct) is a semi-quantitative value that can broadly categorise the
concentration of viral genetic material in a patient sample following testing by RT
PCR as low, medium or high. It tells us approximately how much viral genetic
material is in the sample.
There over 80 different commercial PCR tests and several platforms used in the UK.
Each comes with its own standardised interpretation. Some may provide Ct values
some may not. Therefore, Ct values cannot be directly compared between assays of
different types. All labs are asked to perform preliminary checks on the limits of
detection and create a standard operating procedure based on guidance above to
interpret a positive or negative result.
The Medicines and Health Products Regulatory Agency (MHRA) is the national
regulator for medical tests and any test can legally be marketed and deployed in the
UK once it receives a CE mark. For further information refer to this link here:
If you have any queries regarding the information that has been supplied to you,
please refer your query to me in writing in the first instance. If you remain dissatisfied
and would like to request an internal review, then please contact us at the address
above or by emailing firstname.lastname@example.org.
Please note that you have the right to an independent review by the Information
Commissioner’s Office if a complaint cannot be resolved through the PHE
complaints procedure. The Information Commissioner’s Office can be contacted by
calling the ICO’s helpline on 0303 123 1113, visiting the ICO’s website at www.ico.org.uk
or writing to the ICO at Wycliffe House, Water Lane, Wilmslow,
Cheshire, SK9 5AF.