As the coronavirus pandemic continues, people are turning to home testing kits for clarity and peace of mind. However, there have been doubts around the accuracy of such tests.
Experts have warned that if at-home tests are not carried out correctly, sampling errors could give false negative results.
Speaking to the BBC, national testing coordinator, Professor John Newton, explained that, while home tests are as accurate as drive-in health centre tests, “No test is perfect.”
“A negative test is a good guide, but it’s not an absolute guarantee that you are free of the virus so we just need to be aware of that,” he added.
Professor Lawrence Young, a virologist and expert in molecular oncology from Warwick Medical School, told HuffPost UK, “The way you take the sample with swabs in the nose and throat is very inaccurate - and indeed, having seen some of this on the TV where people are driving into these testing centres and you see the swabs being taken, I’m very concerned they’re not actually swabbing correctly.”
What does the test involve?
The government website explains that the testing process “usually involves taking a swab of the inside of your nose and the back of your throat, using a long cotton bud.”
“You can do the swab yourself or someone can do it for you,” the official advice reads.
How to correctly take a nasal and tonsil swab sample
One main error in the testing process is touching the cotton swab with your tongue, when aiming to reach the tonsils.
Speaking to The i, teacher Nick Hart (who had a test at a health centre in Crawley, West Sussex) said, “This is a complicated procedure with numerous steps and there are multiple possibilities for it to be done incorrectly, for example if the swab touches your tongue rather than your tonsils.”
To avoid touching your tongue during the sample collection, try using a mirror to guide your hand holding the swab, while using your free hand to hold your tongue down with a clean tongue depressor.
Equally, it may help to have someone else administer the test for you.
The Private Harley Street Clinic has published a full list of instructions were online, including the following instructions:
- Ensure hands are clean
- Insert swab into mouth avoiding tongue
- Brush the swab repeatedly at the back of the throat over posterior pharynx and tonsillar areas avoiding the tongue
- Then insert the same swab approximately 2cm into one nostril
- Gently rotate inside the nostril for three to five seconds. Repeat the process for the other nostril, using the same swab
When should I take the test?
The government website advises the public to “have the test in the first 5 days of having symptoms.”
“It's best to ask for the test in the first 3 days, as it may take a day or two to arrange,” it reads.
This advice is given because the virus travels around the body of the infected person, moving from the nasal passage or the back of the throat in the early days of the infection, and down towards the lungs in the later stages.
Dr James Gill, a GP locum and honorary clinical lecturer at the University of Warwick said, “The longer you have the condition, the virus migrates and it goes down into your lungs.
“So, even though you’re coughing, you’ve got the fever, we might not be able to get the swab because it might not be there anymore. It might’ve gone down to the lungs. That’s one reason we can miss it.”
How can I get a test?
In the House of Commons on Monday 18 May, Health Secretary Matt Hancock said, “We are expanding eligibility for testing further than ever before.
“Anyone with a new continuous cough, a high temperature or the loss or change of sense of taste or smell can book a test by visiting nhs.uk/coronavirus.”
However, the government website states, “Even if you are successful in requesting a test, we cannot guarantee you will get one. It depends on how many tests are available each day in different parts of the country.”