FOI Ref: FOI/2022/3802
1.How accurate are the PCR tests?
2.How accurate are the lateral flow tests?
3.Has Covid-19 or any other variants been isolated or purified?
4.What steps are in place to identify the virus and different variants?
5.What testing equipment do you have in place to distinguish between for example Covid 19, delta and Omicron please?
Thank you for your request.
The COVID-19 Infection Survey is a household survey that estimates the number of people testing positive for infection and for antibodies in the UK. Our statistics refer to the number of current COVID-19 infections within the population living in private residential households. We exclude those in hospitals, care homes and/or other communal establishments. In communal establishments, rates of COVID-19 infection are likely to be different.
The COVID-19 Infection Survey only uses RT-PCR tests. You can find information about the accuracy of these tests in our COVID-19 Infection Survey: methods and further information article under the subheading Test sensitivity and specificity. Test sensitivity measures how often the test correctly identifies those who have the virus, so a test with high sensitivity will not have many false-negative results. Studies suggest that sensitivity may be somewhere between 85% and 98%. Test specificity measures how often the test correctly identifies those who do not have the virus, so a test with high specificity will not have many false-positive results. We know the specificity of our test must be very close to 100%.
We do not hold information on the accuracy of lateral flow tests. Please note that the UK Health Security Agency (UKHSA, previously Public Health England) are responsible for NHS Test and Trace. For more information on PCR and lateral flow testing in Test and Trace you can visit the government's coronavirus (COVID-19) dashboard or contact UKHSA at firstname.lastname@example.org.
We do not hold information on the isolation and purification of COVID-19. The UKHSA may be better placed to answer your query and can be contacted via email at email@example.com.
Q4 and 5)
To test for the presence of the virus, the nose and throat swabs collected are sent to the Lighthouse laboratory in Glasgow and are tested for SARS-CoV-2 using reverse transcriptase polymerase chain reaction (RT-PCR). RT-PCR tests alone cannot distinguish between variants. However, they can be useful indicators of the variant when taken in conjunction with other data. For more information on how we identify variants via RT-PCR tests in the study, please see 'section 4: study design: processing the data' in our Coronavirus (COVID-19) Infection Survey: methods and further information article. In the technical dataset accompanying our latest Coronavirus (COVID-19) Infection Survey bulletin, on tab 1c, you can find the modelled daily rates of the number of cases compatible with Omicron BA.1 and not compatible with BA.1 for each of the four UK nations.
The only way to precisely identify a variant is genome sequencing -- where the virus detected on a swab undergoes a detailed investigation to work out all the letters in its genetic code. The virus genetic material from every positive swab in the survey with sufficient virus (cycle threshold (Ct) value less than 30) is sent for whole genome sequencing at Northumbria University.
In the technical dataset accompanying our latest Coronavirus (COVID-19) Infection Survey bulletin, you can find the genetic lineages in the sequenced samples in the COVID-19 Infection Survey in tab 1e. For more information about whole genome sequencing, please see 'section 4: study design: processing the data' in our Coronavirus (COVID-19) Infection Survey: methods and further information article.
Further information and an overview of data about the coronavirus (COVID-19) pandemic from the Office for National Statistics (ONS) and other sources can be found in our Coronavirus (COVID-19) latest insights tool.