FOI Reference: FOI/2021/2974
You asked
Please supply the recorded date when the Office of National Statistics (ONS) started recording the Cycle Threshold (Ct) values that are associated with the positive test results (i.e. "cases") in the polymerase chain reaction (PCR) test that is used to detect "COVID-19" and/or infection with the SARS-CoV-2 virus.
For the avoidance of doubt the Cycle Threshold (Ct) value is the number of deoxyribose nucleic acid (DNA) amplification cycles following the Reverse Transcriptase (RT) stage of the test that coverts ribose nucleic acid (RNA) into DNA for amplification i.e. the Ct value is a positive integer.
It is understood by the requester that the different RT-PCR tests that are used by different test sites will have different Ct value criteria to define a "positive case" (i.e. the number of DNA amplification cycles before there is a signal of sufficient strength to define a positive test) however this request simply asks for the date when the raw data for Ct values was recorded by the ONS along with the data of the positive test result, if this date exists at all.
We said
Thank you for your request.
The COVID-19 infection survey has recorded Ct values since the survey began on 26 April 2020. We began publishing the Ct values of positive tests from the 21 September 2020. In the technical dataset accompanying our latest bulletin, you can find the percentages of positive cases by Ct value in the UK on tab 1a.
For further information and an overview of data about the coronavirus (COVID-19) pandemic from the ONS and other sources, please check our latest insights tool.