This is an HTML version of an attachment to the Freedom of Information request 'Pcr tests'.

Public Accountability Unit 
  T  020 8327 6920 
Wellington House 
133-155 Waterloo Road 
London SE1 8UG  
By email 
Our ref: 09/03/tr/3000 
07 April 2021 
Dear Meric Kesic, 
Re: Vaccination data among health care workers 
Thank you for your request received on 09 March 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 hold some of the information you 
have specified. I have responded to your requests in the order raised:- 
1)  What information have you got on the pcr tests ability to know the 
difference between covid19 and any other coronavirus? 
A range of different PCR assays are being used by Public Health England for the 
detection of the Covid-19 virus. The specificity of each test is carefully evaluated 
including the ability to detect the Covid-19 virus (including variants) and to 
distinguish these from other coronaviruses. The specificities of the assays used are 
available from the individual manufacturers who are responsible for their production. 
Evaluations are also available in the peer reviewed scientific literature including that 
originally produced by an international scientific consortia which included staff from 
PHE and is available from the reference given below:        
Corman VM, Landt O, Kaiser M, Molenkamp R, Meijer A, Chu DK, Bleicker T, 
Brünink S, Schneider J, Schmidt ML, Mulders DG, Haagmans BL, van der Veer B, 
van den Brink S, Wijsman L, Goderski G, Romette JL, Ellis J, Zambon M, Peiris M, 
Goossens H, Reusken C, Koopmans MP, Drosten C. Detection of 2019 novel 
coronavirus (2019-nCoV) by real-time RT-PCR. Euro Surveill. 2020 
Jan;25(3):2000045. doi: 10.2807/1560-7917.ES.2020.25.3.2000045. Erratum in: 
Euro Surveill. 2020 Apr;25(14): Erratum in: Euro Surveill. 2020 Jul;25(30): PMID: 
31992387; PMCID: PMC6988269. 
2)  What information have you got on why you test for coronavirus (flu and 
common cold) and not covid19? 
Public Health England performs a very wide range of tests for human pathogens 
including viruses transmitted via the respiratory tract (influenza, covid-19 and other 
coronaviruses). Data is published through periodic surveillance updates on the PHE 
website and in specific studies. Two examples of specific studies are given in the 
references below: 

Beale S, Lewer D, Aldridge RW, Johnson AM, Zambon M, Hayward A, Fragaszy E. 
Household transmission of seasonal coronavirus infections: Results from the Flu 
Watch cohort study. Wellcome Open Res. 2020 Jun 19;5:145. doi: 
10.12688/wellcomeopenres.16055.1. PMID: 33553677; PMCID: PMC7848853. 
Aldridge RW, Lewer D, Beale S, Johnson AM, Zambon M, Hayward AC, Fragaszy 
EB; Flu Watch Group. Seasonality and immunity to laboratory-confirmed seasonal 
coronaviruses (HCoV-NL63, HCoV-OC43, and HCoV-229E): results from the Flu 
Watch cohort study. Wellcome Open Res. 2020 Dec 10;5:52. doi: 
10.12688/wellcomeopenres.15812.2. PMID: 33447664; PMCID: PMC7786426. 
3)  What information have you got about the false positive rates for the pcr 
No diagnostic test is 100% accurate, false positives and false negatives can occur 
depending on a number of factors not directly related to the test performance. Once 
in use, the performance of the test is continually monitored and reviewed for 
technical quality and performance. PHE is very aware of the risk of false positives 
where prevalence is low in the population being tested and is working with all Pillar 1 
and Pillar 2 labs to put in place measures to reduce that risk including ensuring that 
appropriate CT values are being used and that where appropriate samples are re-
tested to ensure results are as accurate as possible. Further information can be 
found through the following link -
Daily reported case numbers exclude results that have been identified as false. 
In June 2020 the Scientific Advisory Group for Emergencies published a briefing 
paper on the impact of false positives and false negatives in the United Kingdom’s 
COVID-19 reverse transcription polymerase chain reaction (RT-PCR) testing 
The briefing paper states that the United Kingdom operational false positive rate is 
unknown, and an attempt has been made to estimate the likely false-positive rate of 
national COVID-19 testing programmes by examining data from published external 
quality assessments (EQAs) for RT-PCR assays for other ribonucleic acid viruses 
carried out between 2004-2019. Results of 43 EQAs were examined, giving a 
median false positive rate of 2.3%. The paper can be accessed here:
4)  What information have you got about the cycle rate of the pcr 
The Cycle Threshold varies between the various platforms used within each testing 
laboratory, and is not therefore uniform. There is correlation between some Platform 
types, where all parts of the process are similar. Every PHE laboratory has 
determined the limit of detection for SARS-CoV-2 across all assays used for patient 
testing. Additionally, every PHE laboratory has in place a strategy for the 
confirmation of positive results when the screening result was above the threshold 
identified in the screening assays. 
PHE does not hold this information for non-PHE laboratories. Many laboratories 

contribute to the government’s testing programme and PHE does not maintain 
central records of testing undertaken in each lab. 
Under Section 16 of the FOI Act, public authorities have a duty to provide advice and 
assistance. Accordingly, you may wish to contact the Department of Health and 
Social Care, which may be able to advise further. The contact details can be found 
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  
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 or writing to the ICO at Wycliffe House, Water Lane, Wilmslow, 
Cheshire, SK9 5AF. 
Yours sincerely  
FOI Team