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Highland public health director: Here's why Covid testing remains vital right now


By Andrew Dixon

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Dr Tim Allison, director of public health for NHS Highland.
Dr Tim Allison, director of public health for NHS Highland.

Testing for the Covid virus has been vital in efforts to control the pandemic.

More attention has rightly been paid to the development of Covid vaccines than to the development of tests, but the opportunity to find out whether people are infected with Covid remains crucial.

We do not have to rely just on symptoms to find out if someone is infected with Covid and this is important since many people don’t have symptoms when they are infected but can still infect others.

Effective tests have been available almost since the start of the pandemic, but the difference between tests and their correct use still causes confusion.

I have written about testing before, but there is no harm in repeating some things and I also want to emphasise the most important messages.

There are three main types of Covid tests: PCR, lateral flow devices (LFD), and antibody. They all test for Covid, but they work in different ways.

Antibody tests are used to measure the body’s reaction to Covid, and their use is mainly confined to research studies.

PCR tests can identify tiny quantities of the genetic material from the virus and have a high degree of accuracy in determining if someone has the virus. They need to be analysed in a laboratory and people can still test positive for weeks after an infection.

Lateral flow devices or lateral flow tests give results in minutes at home but they need to detect more virus material to give a positive result and so they are less sensitive than PCRs. Because LFD tests need more virus to become positive they are good at showing when people are infectious with Covid but they are not good at identifying people who are not infected.

If you have no symptoms and want to check out if you are infectious so that you can protect other people, then take a lateral flow test.

Used Lateral Flow Tests during Coronavirus COVID-19 Pandemic
Used Lateral Flow Tests during Coronavirus COVID-19 Pandemic

Tests are available from pharmacies, by mail and at many other locations. Perhaps you are going to meet people or go on public transport, or you may be asked to take tests for work. If the test is positive, then you must isolate since this shows evidence of Covid infection.

Even a faint line by the letter T on the testing device means that it is positive. One positive test is all you need, so if the first is positive don’t take another to check.

If you have symptoms of Covid then book a PCR test. Symptoms include the three classic Covid symptoms of cough, temperature or loss of taste or smell.

Covid can also produce other symptoms and it seems that the Omicron variant can frequently give symptoms similar to the common cold. If you have symptoms, you cannot rely on a negative lateral flow test and you need a PCR.

If we all understand and use the right Covid test, we will be playing our part in the overall effort to help others and support health and social care.

Dr Tim Allison is NHS Highland’s director of public health and policy.


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