Since the start of the COVID-19 pandemic we have been receiving enquiries about testing. This blog provides the answers to some of these questions, and was last updated on 3 December 2020.
What is the difference between coronavirus, COVID-19 and SARS-CoV ?
Each of these terms are often used interchangeably but they are actually quite distinct. Coronaviruses are a family of viruses that range from the common cold to MERS (Middle East Respiratory Syndrome) and SARS (Severe Acute Respiratory Syndrome).
SARS-CoV-2 stands for Severe Acute Respiratory Syndrome Coronavirus 2 and is a new type of coronavirus. It is this specific virus which causes COVID-19, the name given to the resulting disease. In naming the disease “CO” comes from corona, “VI” comes from virus, “D” comes from disease and “19” comes form 2019, the year when the first cases were seen.
What test is used to detect COVID-19?
The most commonly used test to date is the ‘PCR’ test. PCR stands for Polymerise Chain Reaction and these tests work by detecting the genetic material of the actual SARS-CoV-2 virus. PCR tests are used to determine whether someone is actively infected with the virus and therefore they are useful in guiding whether people should self-isolate, and for tracing their contacts to break the chain of transmission.
Who can be tested in Scotland?
The Scottish Government published its updated testing strategy on 17 August 2020. This outlines the Scottish Government’s testing priorities:
- Testing of anyone with symptoms of COVID-19
- Proactive case finding by testing contacts and testing in outbreaks.
- Routine testing in high risk settings, such as care homes.
- Testing people prior to receiving healthcare
- Surveillance testing to monitor prevalence
Symptomatic people in Scotland need to get the test done in the first five days of having symptoms. (In England and Wales this has been expanded to eight days).
The Scottish Government has also published Guidance on coronavirus testing this includes information on who is eligible for a test, how to get tested and the different types of test available.
How do I get a test?
Information on how to get a test for COVID-19 can be found on the NHS inform website or by calling 0800 028 2816.
Can I get a test for travel purposes?
Only people who work in certain roles and need to travel for work will be tested. NHS inform notes that this includes those who work in care homes and selected groups of healthcare workers, and only if this has been agreed as a policy or occupational health decision.
If someone needs to prove that they don’t have COVID-19 as a condition of travel it is possible to obtain a PCR test and travel certificate from a number of private companies.
A public screening centre for COVID-19 has recently been established at Edinburgh airport. People will be able to pay for a PCR test and receive the test results the next day.
Can I get a test to reduce the amount of time I have to isolate for when returning to Scotland?
The UK Government has announced a test to release scheme which will start from 15 December for people traveling to England. Under the scheme people can pay for a private COVID-19 test to be taken at least five days after they have left a destination not on the travel corridor list for England. If the result is negative they can stop isolating rather than having to continue to isolate for 14 days from departure.
This is currently not being rolled out in Scotland although a Scottish Government spokesperson has been reported as saying:
We recognise the impact that the pandemic has had on airports and airlines and we are exploring alternatives to quarantine that will minimise the risk to public health. We are aware of the UK government’s plans to introduce test to release and we are working with the main commercial airports in Scotland and clinical advisors to understand the risks and benefits of such an approach here. We are currently assessing if test to release can be implemented in a way that minimises risk, which includes understanding the capacity of private sector labs to conduct testing to a minimum standard as well as determining the best time for a pilot of this nature.
How accurate are PCR tests?
The Clinical and Scientific Review of the Scottish Government Testing Strategy states that:
The current gold standard test for the COVID-19 virus is PCR testing…PCR testing has been very effective in the management of symptomatic disease to diagnose COVID-19 as it detects the presence of the causative agent in the context of symptoms that indicate possible infection. It is sensitive (it has a low false negative rate) and specific (a low false positive rate).
The BMJ in its article on interpreting COVID-19 test results notes that the accuracy of PCR swabs in clinical practice varies depending on the where the swab is taken from and the quality of sampling.
What is sensitivity and specificity?
When describing the accuracy of a test the terms “sensitivity” and “specificity”are used.
- Sensitivity: is the proportion of people with SARS-CoV-2 infection who test positive. A test with sensitivity of 95% would mean that 5 in 100 people who have COVID-19 would test negative (false negative). They have an infection, but the test says that they don’t.
- Specificity: is the proportion of people without SARS-CoV-2 infection who test negative. A specificity of 90% means that 10 in 100 people who are not infected still test positive (false positive). They do not have an infection, but the test says that they do.
Test sensitivity and specificity is reported by manufacturers by seeing how good their test is at confirming the results for a group of samples that are already known to be positive or negative.
Table 2 in the article Molecular and Serological Tests for COVID-19. A Comparative Review of SARS-CoV-2 Coronavirus Laboratory and Point-of-Care Diagnostics shows the results of an independent evaluation to verify the clinical performance of several tests.
The House of Commons Parliamentary Office of Science and Technology has published a useful articles on interpreting COVID-19 test accuracy.
Do PCR tests pick up viruses other than SARS-CoV-2?
Full Fact has looked at the possibility that a test might pick up viruses with generic similarities – known as cross-reactivity. It said this:
is something that is looked at when designing PCR tests. For example, one of the earliest PCR testing protocols, which was published on 13 January, specifically checked that the test did not pick up the four human coronaviruses that cause infections including the common cold. Results for a range of available PCR tests show that they do not cross-react with any viruses analysed, including other coronaviruses.
Table 3 in the article Molecular and Serological Tests for COVID-19. A Comparative Review of SARS-CoV-2 Coronavirus Laboratory and Point-of-Care Diagnostics gives the analytical specificity of the tests with respect to cross reactivity with other pathogens than SARS-CoV-2.
What are the limitations of the PCR test?
The Clinical and Scientific Review of the Scottish Government Testing Strategy comments that all tests have some limitations. One of the limitations of the PCR tests is that they take time to be analysed as samples need to be extracted and the PCR reaction takes time.
With all tests there is also a possibility of the test giving false negative results or false positive results – this is explained above.
Are there new tests on the horizon?
The House of Commons Parliamentary Office of Science and Technology has published a useful article on the latest in COVID-19 testing: developing new technologies.
What about rapid testing?
In a debate on 25 November 2020 on the roll-out of the COVID-19 testing programme, the Cabinet Secretary for Health and Sport, Jeane Freeman MSP. provided an update on the expansion of COVID-19 testing and the use of lateral flow devices.
Lateral flow tests are rapid turnaround tests that can process COVID-19 samples on site without the need for laboratory equipment, with most generating results in under half an hour.
They have been evaluated by Public Health England and the University of Oxford for use in mass community testing.
However, some experts warn that the tests may miss as many as half of covid-19 cases, depending on who is using them – making them unsuitable for a “test and release” strategy.
How is COVID-19 testing being expanded?
In a debate on 25 November on the roll out of COVID-19 testing programme, the Cabinet Secretary for Health and Sport, Jeane Freeman MSP, provided an update on the expansion of COVID-19 testing. She outlined the expansion of testing for:
- university students
- school staff
- admissions to hospital emergency departments, acute assessment centres, maternity unity and emergency mental health units – with the intention to extend to all medical and surgical admissions by mid-December
- healthcare workers
- care home residents and visitors
- home care workers – from mid-January.
In relation to community testing she said:
Our testing capability now enables us to work with local partners to trial whole-community testing in exactly those areas where transmission has stayed stubbornly high. Next week, we will be deploying up to six additional mobile testing units and 20,000 home test kits to support work in five local authority areas: Glasgow City, Renfrewshire, East Ayrshire, South Ayrshire, and Clackmannanshire.
We will also set up an asymptomatic test site using lateral flow testing in Johnstone in Renfrewshire, which has one of the highest numbers of new cases per 100,000 people of any local authority in Scotland. That centre will have capacity to test up to 12,000 people a week.
In her statement on 1 December 2020, the First Minister provided additional information stating that:
testing is now available for people without symptoms of Covid, in several communities across Scotland which have had high levels of the virus. For example test sites opened yesterday in Dalmarnock and Pollokshields in Glasgow; in Stewarton in East Ayrshire; and in Girvan in South Ayrshire. Another site opens tomorrow in Johnston in Renfrewshire.
These trials will inform our plans to expand community testing early in the new year – which we hope will be a useful additional tool in reducing prevalence of the virus in areas with high transmission rates.
What is antibody testing?
An antibody test looks at whether someone has had COVID-19 by detecting a person’s immune response to the SARS-CoV-2 virus. These tests are being used in surveillance and research programmes to find out how many people have had the infection or to study the immune response to infection.
Antibody testing is being used in Scotland for population research and, where appropriate, clinical management of patients. People can request an antibody test but this will be at the discretion of your clinician and depend on whether this will affect your treatment or clinical management.
What is genetic sequencing?
The Scottish Government’s testing strategy outlines that genome sequencing of the COVID-19 virus is currently being undertaken by a Glasgow and Edinburgh partnership working as part of the COVID-19 Genomics UK (COG-UK) Consortium. Whole Genome Sequencing contributes to the understanding of how the disease moves through the population and changes over time.
How much has the Scottish Government provided to health boards to expand COVID-19 laboratory testing?
In response to a Freedom of Information request the Scottish Government provided a breakdown of the initial provision for NHS Boards for NHS Test and Protect, on 6 November 2020. The response noted that activities and costs remain under close review and funding to Boards will be revised through the year in line with agreed changes.
NHS Ayrshire and Arran
NHS Dumfries and Galloway
NHS Forth Valley
NHS Greater Glasgow and Clyde
NHS Western Isles
National Services Scotland
Public Health Scotland
Lizzy Burgess. Senior Researcher, Health and Social Care