Anyone who has tried using the free lateral flow test kits provided by the UK Government will no doubt agree – collecting a swab from your tonsils is not a pleasant experience!
And while the nose (nasal) part of the swab collection is not pleasant either, especially if you insert the disposable swab 2.5cm into your nostril as recommended, it is the gag-reflex (pharyngeal reflex) caused by the throat swab that most people hate the most.
So with manufacturers like Hughes Healthcare and Swiss Point of Care selling alternative nose-only lateral flow test kits for SARS-CoV-2 are these as safe and accurate as the full Nasopharyngeal (nose and throat) tests that the Government are providing?
Key Takeaway: Nasal Swab Lateral Flow Tests Win On Comfort
Certainly, with key workers, secondary school students, and parents of all school children being asked to do twice weekly swab tests, a nose-only option is going to be the preferred choice of many, even if they have to buy them rather than being provided with them free of charge, but are they approved, do they work as well, and can they be trusted?
CE Mark Approval
Both the Hughes Flowflex test kits and the Swiss Point of Care test kits (both of these are nasal lateral flow tests) carry the prized CE mark approval, and so do the Roche nasopharyngeal rapid covid tests. So the 2 main types of coronavirus lateral flow test kits that we sell both score the same when it comes to CE Mark approval.
Accuracy, Specificity, and Sensitivity
A high specificity rating means that a coronavirus test is not likely to produce a false positive. For example, the Hughes Flowflex nasal test kits have a specificity of 99.5%, which means that there is a 0.5% chance of a false positive. This compares with 99.6% for the Roche test kits, so the nasopharyngeal wins in this comparison, although the difference is very slight at 0.1% difference. The most recent data from the gov.uk website indicates even higher specificity rates for LFD lateral flow tests – see this UK government press release.
The sensitivity of lateral flow tests depends a lot on the viral load of the person infected with the Coronavirus. High viral loads give high levels of sensitivity, with over 97.1% of cases being picked up by the Hughes nose-only swab test kits, and 95% of covid cases being detected by the Roche nose and throat swab test kits. So on sensitivity, nasal rapid covid test kits are the winner, but again, the margin of difference is small. This government article states “Lateral flow tests deployed in Liverpool shown to have over 99.6% specificity” but also states “an overall sensitivity of 76.8% for all PCR-positive individuals but detects over 95% of individuals with high viral loads, and minimal difference between the ability of the test to pick up viral antigens in symptomatic and asymptomatic individuals” – again showing how good LFD tests are for people with high viral loads, but how the PCR lab tests are the ones to take if the viral load is lower.
Viral loads are very high initially, often before symptoms appear, but can decline rapidly over the first few days of infection, meaning that by the time your symptoms are obvious, a lateral flow test is less likely to pick up the virus and a PCR test is the government’s recommendation at that stage, in fact, the government are currently only offering lateral flow test to people who do not have symptoms.
The combined measures of sensitivity and specificity are used to determine the overall accuracy of lateral flow tests, as set out in this piece of government research. With our nasal swab tests scoring better on sensitivity, and our nasopharyngeal swab tests scoring best on specificity, we conclude that the overall accuracy measure is pretty much a tie, especially considering the small margin of difference on both accuracy measures.
See below chart comparing the accuracy of both types of test:
|Roche COVID test||99.6%||95.0%*|
|Hughes COVID test||99.5%||97.1%|