The way the government’s coronavirus dashboard tells it, we can hardly move for covid lateral flow tests. Back of the envelope sums suggest there are now ‘only’ 600,000 plus daily LF tests, down from a peak of around a million daily tests in mid March. It’s a wonder we aren’t awash with grimy discarded test kits, jetsam from the ghost ship the New Normal. In Australia, where they take these things very seriously, the jetsam could have been far worse. A few months back, a zeroid (an endemic-covid denialist who believes instead in zero-covid, whatever it takes, and whatever it means) suggested that adding anal swabs for kids — zeroids believe kids and schools are hotbeds of infection and transmission — might pick up the covid that other tests can’t reach. What could possibly go wrong?

The zeroid  back pedalled furiously when the proverbial hit the twitter fan, claiming that she had never meant to suggest anal swabs should be used for mass testing in children. Tweet 17/22, the deleted tweet, is ambivalent, because of the disjointed nature of twitter threads, but the paper the twitter thread summarises does suggest anal swabs in children might be a “useful adjunct in household contact studies”, which as it stands is not mass testing. But that didn’t stop twitter users from recognising one of the universal laws of the New Normal: that a covid test, once unleashed on the public, naturally expands to fill the available space.

Nowhere do we see that law in operation than in the investigation, authorisation and roll out of covid lateral flow tests. By late November last year, preliminary results from the Liverpool mass lateral flow test pilot showed the tests were duds for all so called ‘test-to-enable’ uses, that is green light an individual to undertake some activity. With a positive PCR test as the benchmark, lateral flow tests picked up just under half of the PCR positives, or putting it the other way round, the lateral flow tests missed just over half of the PCR positives. Putting aside the necessary caveat that the PCR test is an oversensitive benchmark, the 30 minute no lab lateral flow test for PCR positives is on a par with an even simpler 30 second test, tossing a coin. Heads you are a PCR positive, tails you are not. Or it might be the other way round.

Needless to say, no such trifles were to get in the way of granting emergency use approval for the DHSC repurposed Innova lateral flow test. In a bizarre letter dated 22nd December 2020, the Secretary of State for Health, acting as the MHRA, is reported to have granted himself, or rather his department, ‘Authorisation of Special Use of DHSC Covid–19 Self-Test Kit’, albeit with a long list of conditions attached. Among other things, these specifically exclude ‘test-to-enable’ use, and appear to sanction only ‘red light’ use, where an individual with a positive test suffers consequences. All too soon, as we shall see, these conditions were ignored, as the authorisation triggered the universal law of covid–19 tests, that once unleashed on the public, the test expands to fill the available space.

In the meantime, the University of Liverpool published its interim evaluation report into the Liverpool Covid–19 Community Testing Pilot of community open-access testing for the Covid-19 virus SARS-CoV-2 among those without symptoms. This showed the Innova test sensitivity was even ‘lower than expected’, at around 40%, meaning that PCR positive punters would get a more accurate result from tossing a coin than taking a lateral flow test, but hey-ho, let’s not let that get in the way of a stonking good roll-out. The interim report also revealed some other serious flaws, notably that far from reaching the virus that other tests can’t reach, the test was clearly failing to get to those most at risk, with uptake in deprived areas running at half the rate in the least deprived areas, despite the fact that the positivity rate was twice as high in the most deprived areas when compared to the least deprived areas. Adding another bent nail to the invisible coffin, the report also noted that “there is no clear evidence that the introduction of ‘mass’ testing in Liverpool impacted on Covid-19 cases or hospital admissions”. Not so much, then, a question of what could possibly go wrong, as can anything possibly have gone right?

Back to the lateral flow test roll-out, and the million tests a day in March. This of course coincided with the return to school, and the tests — which the SoS acting as the MHRA in his authorisation had explicitly said should not be used as tests-to-enable — were now rapidly expanding to fill the available space, as satchels up and down the land filled up with lateral flow test kits. Ostensibly, these were red light tests, in that only positive tests had consequences, but that is a nonsense. A negative test is implicitly a green light test-to-enable test, in this case to enable school attendance. In April, this schools guidance was withdrawn, and replaced with even broader guidance, that made lateral flow tests available to anyone without covid symptoms who fancied one and couldn’t get a test by other means. At the same time, the Events Research Programme explicitly introduced lateral flow tests as green light test-to-enable attendance tests for sporting, music and other events. The tests had fulfilled the law of covid–19 tests, and expanded to fill the available space.

Yet the tests are remain explicitly unauthorised for green light test-to-enable testing. Their real world sensitivity, estimated to range from 3% to 40% using the PCR positive benchmark, renders them useless for green light testing, as at least 60%, and possibly as many as 97% of PCR positives will get a negative lateral flow test, and so a green light. To rightly ban the use of covid lateral flow tests as unworthy of mass green light testing, only then to roll out mass green light testing for the masses, truly this is the work of a remarkable Secretary of State working in remarkable times. All the people had to do was go with the flow, and, as the government’s coronavirus dashboard tells us, that is exactly what millions have done. Bad idea. The tests don’t do what they say they do on the tin, but even worse, this is the domestic covid–19 passport coming in through the back door.   


  1. Tom Welsh Reply

    It’a a very strange idea indeed to introduce a “passport” certifying immunity from a disease that has no unique signs or symptoms, and for which there is no reliable test.

    Very much indeed like witch-finding, actually.

  2. dearieme Reply

    Putting aside the necessary caveat that the PCR test is an oversensitive benchmark

    But why put it aside? It seems we have two different tests, neither of which we can be confident in.

    It’s remarkable that “we” have developed four different effective vaccines in the last 12 – 15 months, but not an effective test for infection. “We” have identified several different effective treatments. But still no decent test. Why not?

    • dr-no Reply

      The putting aside the over-sensitivity is only in the context of using it as a benchmark for assessing LFTs – in every other situation, there are very good reasons for putting it aside, or at the very least insisting on sensible use and interpretation, including Dr No’s finding a broken needle in a haystack doesn’t mean you’ve got a sewing machine. It is as well to remember that the engine of the pandemic, and the reaction to it, has been driven almost entirely by testing. Imagine for a moment no one had discovered SARS-CoV-2, and so no one was testing for it. We would have an unexpected and unusual (and it has to be said unexplained) rise in mortality last spring, and then a rather worse than usual bad flu winter this winter, but no worse than those going back twenty years or so. But no testing, no pandemic, no lockdowns, no masks, no vaccines, no authoritarianism, no ruined economy, no ruined education, no huge backlog of NHS elective and semi-urgent work, no ruined social fabric, not even one of them. Perhaps as well as being careful what we ask for, we should also be careful what we test for.

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