There are two types of tests. The antigen test, a throat and nose swab test, tells you whether you currently have COVID-19 infection. Antibody tests are used to detect antibodies to COVID-19 in the blood to see if you have previously had the virus. There is no strong evidence as yet to suggest that those who have had the virus develop long lasting immunity which would prevent them from being infected again.

Antigen testing (for the virus)

The antigen test, using polymerase chain reaction (PCR) technology in a laboratory, tells you if you currently have the virus that causes COVID-19, which is SARS-CoV-2.

Any person with symptoms of COVID-19 (a high temperature, a new, continuous cough, or a loss or change to sense of taste and smell) should self-isolate for at least 7 days. If they do not have symptoms, but a household contact does, they should self isolate for 14 days.

We recommend those with symptoms to apply for a test as soon as possible. Priority testing is available for essential workers. For essential workers we recommend this is arranged here

Coronavirus Briefing Note on COVID-19 Testing and Contact Tracing

Any person in the UK with symptoms can arrange a test through the NHS website here.

Testing is most effective within 3 days of symptoms developing and will not usually be done more than 5 days after symptoms start.

Testing is also available for staff and residents of care homes whether they have symptoms or not. This is applied for here.

For all employees who have had antigen tests, whether they have had tests because they have had symptoms, or have had no symptoms, we recommend a call with occupational health in order to advise on fitness for return to work.

Testing for presence of the virus will make a significant contribution to risk assessment, but no test is 100% reliable; in the case of this test, it is considered that sensitivity (picking up the presence of the virus) is at most 90%. This means that of 100 people tested who actually have the virus, at least 10 will test negative; a false negative.

We have assessed a number of employees with prolonged symptoms that may or may not be due to COVID-19. These symptoms include fatigue, and for some, have lasted weeks.

Our advice is for employees with ongoing symptoms to have a call with one of our occupational health clinicians to advise on return to work. We should emphasise that testing after more than five days from the onset of symptoms is highly unreliable; our advice on return to work is based on how they are. These people are not likely to infect others once symptoms have settled enough for them to be well enough to return to work.

NHS Test and Trace Service

The new NHS Test and Trace service was launched on 28th May 2020. Anyone who tests positive for COVID-19 will be contacted by NHS Test and Trace by text message, email or phone and asked to share information about their recent interactions usually by creating a confidential account on the NHS Test and Trace website. This could include household members and people with whom they have been in direct contact. People identified as having been in close contact with someone who has a positive test must stay at home for 14 days, even if they do not have symptoms. We recommend to our clients that a call is arranged with occupational health for all employees advised to self-isolate for this reason.

If those in isolation develop symptoms, they are advised to book a test at nhs.uk/coronavirus or by calling 119. If they test positive, they must stay at home for 7 days and seek advice (we recommend a call with occupational health) before returning to work. If they test negative, they must complete the 14 days self-isolation period.

Members of their household do not have to stay at home unless the person identified becomes symptomatic, at which point they must also self-isolate for 14 days.

The aim is to reduce spread of the virus, and also allow better understanding of how the virus spreads. This informs control measures to enable us to emerge from lockdown.

It is intended this will be complemented by the NHS COVID-19 App in the coming weeks. This will extend the speed and reach of contact tracing, by helping to identify contacts the individual does not know, e.g. someone next to them on public transport.

Antibody testing (for immunity to the virus)

The antibody test is a blood sample and tests for the presence of antibodies to the COVID-19 virus to see if there is evidence of an immune response to the virus. The Government will be providing laboratory-based tests in the first phase of the antibody testing programme to NHS and social care staff. These tests require blood samples to be taken by trained professionals and are not suitable to be used at home.

The Government is working with the private sector to develop a finger prick test, which will be suitable for use at home, but this has not yet been validated for wide usage.

Unapproved antibody tests should not be used. At present there are no home antibody tests sufficiently reliable to safely inform decisions on risk assessment. It is intended in future these will widely be available, being a key pillar of the Government strategy.

The reason why Government validation of tests is so important is that no test is 100% reliable (the blood sample test now being used for testing health and social care workers is almost 100% reliable). If the specificity (correctly identifying antibodies to the virus) is 98%, this means that of 100 people tested who do not actually have antibodies to the virus, on average 2 will be told they do have antibodies; a false positive. This could then give false reassurance. If there are ten million people tested who do not actually have antibodies, at 98% specificity, on average 200,000 of these ten million will be told they have antibodies when in fact they do not. This is especially important as most people in the UK have not been exposed to the virus (and we want to keep it that way).

Antibody tests tell someone whether they have had the virus, but not about any level of protection or immunity from getting the virus again. The main value of antibody testing is to better understand how COVID-19 has spread, and how we can be best protected.

Testing strategy and plan for your organisation

We recommend any employee who has the result of an antibody test (positive or negative) should have a call with occupational health. We can also advise on antigen and antibody testing as a component of risk management in your organisation.