Note: to reflect the recent changes in availability and eligibility of testing for COVID-19, we will be reviewing this tool. The appearance and content may change according to the findings of this review.

Testing for COVID-19

From the 1st April 2022, the eligibility for getting a free test for COVID-19 in England has changed with many walk in services or pick up points for rapid lateral flow home test kits ending. In addition, most people in England are no longer advised to get tested for COVID-19 (See the NHS England pages for more details on testing).

A small number of people are still able to get free NHS Covid-19 testing. Tests are available for those who are going into hospital for a procedure or surgery or for those with certain health conditions. Patient-facing staff who work in the NHS or in social care are also eligible for free testing. Some local authorities also provide limited supplies of test kits to residents.

Commercial test kits are also available for purchase and there may be requirements for some people to take a COVID-19 test. For example, whilst individuals no longer need to take a COVID-19 test to travel to the UK, some international destinations may require proof of a negative test result. Most commercially available lateral flow test kit results cannot be reported to the UK Government's national reporting system.

As such, the number of people eligible for getting a test and the number of people able to report their test results are now much lower and this will impact case numbers in addition to falling numbers of infections.

The majority of COVID-19 testing in the UK to date has been Polymerase chain reaction (PCR) testing which is lab-based and tests for the presence of SARS-CoV-2 virus (rather than testing for the body's immune response or antibodies). This data shows the number of people who received at least one PCR test in the previous 7 days, as well as the percentage of people who received a PCR test in the previous 7 days who had at least one positive PCR test result (the positivity rate). People are only counted once in a 7 day period.

Lateral flow device (LFD) virus tests are another type of COVID-19 test that look for the presence of SARS-CoV-2 virus. These are also swab tests, like the PCR tests, although they give results in less than an hour, without the need for laboratory processing. LFD tests are generally used for mass and routine testing of people who do not have COVID-19 symptoms. They are aimed at identifying individuals who may be infectious asymptomatic carriers and potential transmitters of the virus so these people can isolate and take the virus out of circulation in the community.

Area PCR Positivity rate (weekly percentage of individuals tested who test positive for COVID-19)

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It is important to consider test positivity with caution and alongside the other measures such as confirmed case numbers and the information available on those being tested.

A higher percentage of positive tests could suggest higher transmission, and perhaps that there are more people with coronavirus in the community who have not been tested yet, which could further indicate a need for conducting a higher number of tests. However, it could also be that a change in positivity is related to different groups of people coming forward for testing. It is likely a mixture of several reasons.

How testing has changed over time

The overall number of virus tests conducted (using lab-based and rapid tests) each day is only available at a national level.

For local areas (West Sussex or its districts and boroughs) we can only see the number of individuals tested using PCR tests in a seven day period or the total number of LFD tests conducted each day. These two measures cannot be combined into a single metric for how many people are being tested and must be considered separately.

The next figure shows how the rolling 7-day number of individuals tested has changed over the course of the pandemic, and particularly how testing ramped up towards the end of 2020.


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The next figure shows the proportion of individuals with a positive result for the same area as in the above barchart. Comparing these two charts helps to contextualise testing. It shows that whilst the number of tests in the early stages of the pandemic were low, a much higher proportion of tests were positive (in some cases around half of tests). In more recent months, many more tests are conducted but fewer of those are positive.

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Whilst the number of individuals tested using the lab-based PCR tests is available for the whole of the pandemic (since February 2020), LFD testing in England only became widely available from the 21st October 2020.

As such, the time period for the next figure (number of LFD tests conducted) is much smaller (for the last few months only). Note also that data are available for very recent days (up to the day before). Whilst test results are much quicker to obtain for LFD tests compared to PCR tests, it is expected that the totals for the last few days will still not be complete due to delays in getting results into the national data systems.


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Note that the PCR and LFD figures are not directly comparable because of the different date ranges.