The UK medical system went into hyper drive after the government cranked up a gear. Therefore testing and tracing attracted top attention, while speed was of the essence. Quick COVID lateral flow tests seemed the answer. However, scientists now have lateral flow testing under the spotlight again. That’s because it failed to detect a third of positive cases in the Liverpool hot spot zone.
British Medical Journal Pins Lateral Flow Testing Under the Spotlight
The occasion was a community testing pilot in the UK’s tenth largest city, with half a million population. Later, British Medical Journal completed a review and concluded:
1… The pilot only detected half as many cases as polymerase chain reaction tests did
2… The pilot also failed to detect three out of every ten cases with higher viral loads
Questions are now being asked how authorities allowed these tests in aged care homes. A Scottish National Party member from across the English border is deeply worried.
‘My main concern is false reassurance,’ he wrote in two parliamentary questions. ‘There is a clear risk that those with a false negative COVID result will feel overly confident. That is, confident about mixing with vulnerable people over Christmas.’
Lateral flow tests are quick, simple ways to identify the presence of a target substance in a liquid. They avoid the need for specialized and costly equipment. However, this convenience comes at the cost of accuracy as we shall see.
Does This Mean We Should Abandon Lateral Flow Testing?
We found an explainer on the Gavi.Com Vaccine Alliance website. We have lateral flow testing under the spotlight, they seemed to say. That’s because we are confusing the twin imperatives of sensitivity and specificity.
1… Firstly, sensitivity refers to the proportion of true positives a test correctly identifies
2… Whereas specificity refers to the proportion of true negatives a test correctly spots
Now, increasing sensitivity comes at a cost of reducing specificity. But low specificity can report a subject infected, while in reality they are clear. While increasing specificity may produce false negative results.
Gavi.Com Vaccine Alliance concedes lateral flow testing can indicate trends in a pandemic. However, their speed and convenience come at the cost of accuracy. Thus extra care is necessary when interpreting and communicating results.
Related
Public Health Risk of Rapid COVID-19 Tests
A Negative Test Is Not a “Drop Your Guard” Card
Preview Image: Lateral Flow Assay Test
Video Share Link: https://youtu.be/z07CK-4JoFo
