Coronavirus: Testing for Covid-19

The World Health Organization (WHO) has strongly encouraged countries to test suspected cases of Covid-19 disease to aid efforts to disrupt the transmission of the SARS-CoV-2 virus and slow the rate of infection. Testing can also help support public health efforts to ‘characterise‘ the disease, so that health authorities can understand its severity, prevalence and how it is evolving.

Types of test

The NHS is using an RT-PCR test to identify cases of Covid-19 in the UK. This relies on collecting genetic material (RNA) from the suspected case via a nose and/or throat swab to detect nucleic acid from the virus. The PCR test can only detect the virus while it is present in the person; it cannot tell if the person has had the virus but has since recovered. The test may also not identify those cases where the person is infected but is not showing symptoms.

‘Serological tests’ for Covid-19 are currently in development. These tests aim to identify whether the individual has previously had the virus – even if they have not shown symptoms – through using a blood or plasma sample to detect if the patient has antibodies to the virus. The Government is reported to have bought options on up to 17.5 million antibody tests, of different types, that could be used ‘at home’ rather than in a clinical setting. The effectiveness of the ‘at home’ serological tests is currently being evaluated. To date, they have not performed well, generating both false negatives and false positives. An antibody testing programme for health and social care staff in England has been in place since the end of May 2020. The programme relies on laboratory-based antibody testing rather than home antibody test kits.

Testing capacity

Testing capacity for Covid-19 has increased during the course of the outbreak, rising from 2,000 tests per day on 5 March 2020 to 12,799 by 4 April 2020 and to over 100,000 by 1 May 2020. The approach to testing has also shifted from a centralised system (where tests were processed by Public Health England laboratories) to a more distributed approach that relies on NHS laboratories, private industry and academia/research institutes. On 2 April, the Health Secretary pledged that the UK would carry out 100,000 tests a day by the end of the month; a target which the Government announced it had met, although the inclusion of home testing has been contested. The Government subsequently committed to increase testing capacity to 200,000 tests per day, across the UK, by the end of May and then to 500,000 by the end of October 2020. The Government announced that the 200,000 target had been reached on 30 May 2020, while the Department of Health and Social Care has reported that the Government is “on track” to meet the 500,000 target.

The Government has been subject to criticism for not scaling up the UK's testing capacity earlier, and more rapidly, and for failing to prepare sufficiently for the pandemic. Several reasons have been cited as to why testing capacity was not higher during the early stages of the pandemic, including shortages of the key materials that are needed to perform and run the tests. Since late August 2020, there have also been reports that demand for tests in the community has been outstripping supply, with some people unable to access a test close to their home. Limits on laboratory capacity, together with people who are not eligible for a Covid-19 test being tested, have been identified by the Government as two of the causes of the capacity problem.

Criteria for being tested

At the start of the outbreak, the UK pursued a testing and contact tracing policy which aimed to ‘contain’ the virus and disrupt transmission through testing suspected cases and following up with the close contacts of those who tested positive. As the UK moved from the ‘contain’ to ‘delay’ phase of its response to the virus on the 12 March, the criteria for testing narrowed to only the most severe cases. Following criticism that NHS staff were not being tested, the Government announced on the 27 March that testing would be extended to frontline NHS staff in England. On 15 April, the Government announced that staff working in care homes in England requiring a test would be able to access one and that all symptomatic care home residents will also be tested for Covid-19.

Eligibility for testing was subsequently expanded again on 28 April 2020 to include anyone over the age of 65 with symptoms, anyone with symptoms whose work cannot be done from home as well as social care workers and residents in care homes (with or without symptoms). On 18 May 2020, the Health Secretary announced that everyone aged 5 and over with symptoms of Covid-19 was now eligible to be tested. Regular testing for those who are asymptomatic has since been extended to care home staff and residents and, where capacity permits, to frontline NHS staff.

Contact tracing and testing data

The Government has been developing the UK’s contact tracing capabilities and has recruited over 21,000 ‘manual’ contact tracers in England, while also developing an NHS contact tracing app. A ‘Test and Trace’ system in England was launched on 28 May 2020 without the app component (though the app has since been released). The programme aims to ensure that those with symptoms of the virus can access a test quickly and that, if a person tests positive, those people they have had close contact with can be alerted and given advice on the next steps to take. Concerns have been raised, however, about the speed at which test results have been returned, the number of contacts of positive cases being reached, and the extent to which data about confirmed cases is shared with local authorities and local public health teams.