Are saliva-based Covid-19 tests likely to be better for children?

School Covid-19 lateral flow testing has been carried out on a significant scale during the pandemic, particularly in the UK, where many children are tested twice a week, and given free packets of tests to take home for use in the holidays. This has proved useful in mapping outbreaks and to some extent minimising the impact of variants such as Omicron on school populations, so that schools can stay open. Where the UK tests do less well is in terms of usability. At the beginning of the pandemic, children and young people were required to swab both their tonsils and their nostrils, in quite an invasive manner, and then introduce the swab to a vial containing testing fluid, with the resultant mixture dropped onto a test cartridge, rather in the manner of a pregnancy test. Later this changed to just the nostrils, but it is still quite uncomfortable for many children (and indeed adults), and if children are prone to nosebleeds, poking swabs up there every couple of days probably isn’t ideal, particularly if there is an easy alternative.

During my recent sabbatical in Germany as a visiting professor at the Karlsruhe Institute of Technology, I was very interested to see the introduction of pop-up free testing facilities in empty shops and public buildings, run by local pharmacies. These involve the test subject spitting into a small plastic disposable cup which is then tested by a professional. After 15 minutes you are given a certificate stating your Covid-19 status, which then needs to be shown on entry to certain shops, businesses or public buildings, along with your vaccination certificate and your identity card or passport. It is part of their temporary G2+ policy, G standing for Genesen (recovered), Gestestet (tested) and Geimpft (fully vaccinated), which is linked to ICU bed occupancy rates in the region. You currently have to fulfil two of these ‘Gs’ including testing to participate fully in civil society (unless there is a medical exemption).

The simplicity of the German provision led me to wonder why we use saliva tests so rarely in the UK, given how straightforward they can be. I contacted the firm Intelligent Fingerprinting to find out how they operate, and why we don’t see them in British schools. Intelligent Fingerprinting is a spin off of the University of East Anglia, and they mainly produce drug tests that are based on fingerprint sweat, but they diversified during the pandemic. The firm supplied me with a free box of tests to examine as a kind of educational ‘box opening’ (in the manner of box openings for tech gadgets), and told me about how they work.

Outside of the box

The tests are currently sold for professional use only, operating in a similar manner to the nasal/throat tests we have become used to in the UK, but using a saliva swab instead of a nose or throat swab. Bearing that in mind, I found the instructions fairly straightforward, and if these were delivered by volunteers in a school setting, I think they would be easy to follow if people had been given a thorough briefing first. Laying the items out ready for use, I did think it might be easy to touch the wrong end of the test strip by accident if you weren’t used to carrying out the tests, and thought it might have been improved with some sort of DO NOT TOUCH THIS END notice printed in red (although perhaps professionals are more used to this kind of thing than me).

In the box I received, there were:

50 swabs

50 test strips in two sealed packets designed to be closed rapidly after taking out a strip

50 plastic collection tubes with lids

Collection tube holder/rack

Dropper bottle with enough liquid for 50 tests

Laminated image of test strip showing position of Test and Control lines

50 plastic disposal bags for contaminated material

Instructions for use

50 ID stickers

Contents of the box

There was rather less plastic involved in doing tests this way, rather than using cartridges as we have become more used to (Intelligent Fingerprinting test strips are 95% lighter than traditional lateral flow devices), but clearly they need to be used fairly promptly – you have one month after opening the test strip packet to use them all up, so it works in an institutional setting but not in the context of home, not a surprising finding given they are currently for professional use only.

I then carried out the test on myself. It was definitely less intrusive than swabbing tonsils and/or the nostrils, but the swabbing and waiting periods are rather longer for this test than what I have been used to before. I had to put the swab between my gum and cheek and roll it around for two minutes, which is quite a long time for children of school age, and then I was supposed to wait for 20 minutes for a result after adding the solution (lysis buffer) to the tube, mixing it with the sample on my swab by rotating the swab around for 30 seconds, leaving it to soak for 2 minutes, removing the swab, and then adding a test strip.

Soaking my test strip

In the event, I got a Control line result after 4 minutes, and I suspect that if I was riddled with Covid I would not have to wait the full 20 minutes for a Test line either, indicating a positive result (although I did check at 20 minutes to make sure – it remained negative).

Negative result

You can see a video of how it works here:

One very good aspect of the instructions is that there were lots of pictures of what results might look like, with a combination of lines of different strengths, which would make it much easier to deal with than peering at a result and asking someone whether they think that looks like a line (as many people have to do at home at the moment). This process seemed much clearer.

Many different possibilities helpfully explained

The other interesting aspect was that the tests have been trialled in relation to the consumption of different types of common food and medicines, so you don’t have to wait half an hour after eating for them to work successfully.

Overall these tests seemed ideal for a school setting, as long as volunteers had been properly briefed. They probably have particular relevance for primary schools. Yet currently they are only available for use some countries in Europe, the Middle East, and Asia, as well as in the US.

When I asked about the reason for this, I was told that the MHRA recently changed their acceptance criteria for UK approval late in 2021, meaning that Intelligent Fingerprinting would have to carry out a full revalidation of their test if they wanted to be approved to these new criteria. They decided it was not immediately viable, as they had already based the design and validation of the test on the existing regulations, and had been in the process of seeking approval when the rules were changed. They had already managed to gain regulatory approval to sell their CE marked test within all EU territories, so decided to concentrate on those markets instead.

This answered a question that has been annoying me for some time – why British people are opening millions of boxes of tests that are manufactured in China, instead of those procured from businesses based in the UK, which might even be more suitable for the groups they are aimed at, especially when it comes to children, the vulnerable, and the elderly.

If you have views on this, or anything else relating to Covid-19 lateral flow testing of children in school, please feel free to comment below.

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