Lateral flow tests are only accurate in diagnosing coronavirus when administered by trained professionals, as studies have repeatedly shown.
The tests, which give results in just 15 minutes, use nasal or throat swabs. The samples are then mixed in a test liquid and placed in a plastic cassette that can detect the presence or absence of coronavirus, and then an image of a line is created, similar to a pregnancy test, to indicate whether it is positive or negative.
The Department of Health and the NHS are instructing people to do the tests on themselves, although the makers of some kits said they shouldn’t be used as DIY swabs.
Both the smear procedure and the use of the test cassette can easily be performed incorrectly and affect the accuracy of the test.
If the swab is not inserted long enough or deep enough into the nose or throat, it may not pick up any virus fragments. Health professionals may also use nasopharyngeal swabs that reach the back of the nostril, although this is not recommended for people testing themselves.
And if the sample is not properly placed in the cartridge, the result may be incorrect or the display may be incorrectly displayed when generating a result.
SELF-TEST CUTTING ACCURACY FROM 79% TO 58%.
An evaluation of the Innova lateral flow test, widely used in the UK by the University of Oxford and Public Health England, found that its sensitivity – the proportion of positive cases noted – fell from 79 to 58 percent when used by untrained members of the Public instead of laboratory experts.
Based on this assessment, the officers pushed them forward and used them for a real self-test.
PILOT FOUND IN LIVERPOOL LESS THAN HALF THE POSITIVES
When the same Innova test was tested on members of the public in Liverpool – with people taking their own swabs and trained military personnel doing the tests – the swabs picked up only 41 percent of positive cases.
In the study, the rapid tests gave 891 positive results compared to laboratory-based PCR swabs, which found 2,829 positive results in the same group. This means that 1,938 people received a false negative result from the rapid test.
The study didn’t compare this to professionally run rapid tests, but manufacturer Innova claims its test is 95 percent sensitive in laboratory conditions.
… BUT MEDICINE TEST IN SLOVAKIA ‘REDUCED INFECTIONS’
Despite quick side-flow tests that received bad press, officials in Slovakia used them on 5.2 million people – almost the entire population of 5.5 million – in a study that a study later estimated to increase the country’s infection rate by 60 percent to lower.
The tests used were between 70 and 90 percent accurate and all swabs and evaluations were performed by trained medical personnel. They used deep nasopharyngeal swabs that reach the bridge of the nose, while the self-test generally relies only on a nostril swab.
Researchers at the London School of Hygiene & Tropical Medicine said the program successfully screened coronavirus cases that otherwise would not have been found and reduced the number of cases by more than half within a week during a lockdown.
HOW FAST TESTS ARE DIFFERENT FROM LAB-BASED PCR SWABS
Lateral flow tests are an alternative to the gold standard PCR test – scientifically known as the polymerase chain reaction test – which is more expensive and labor-intensive, but more accurate.
A swab is also used in PCR testing, but it is processed using high-tech laboratory equipment to analyze the genetic sequence of the sample and determine if any of them match the genes of the coronavirus.
This is a much longer and more expensive process that involves several types of trained personnel. The analysis process can take hours, with the entire process from swab to receiving the result taking days.
However, it is much more accurate. Under ideal conditions, the tests will be almost 100 percent accurate in detecting the virus, although in the real world this may be closer to 70 percent.