Hello and welcome to more or less on the BBC World Service, with a programme that strives

to help you make sense of statistics so they won't do a number on you.

Over the past year there have been all sorts of disagreements about how to tackle the coronavirus

pandemic, but recently an exceptionally ferocious row has broken out among an unlikely group

of people.

You get these sort of really senior scientists and you know, you know, spios statisticians

and epidemiologists and professors of medicine and all that sort of stuff and they're all

calling each other negligent and deranged.

So yeah, it is certainly the most savage row I've remembered reporting on.

And he should know this is Tom Chivers.

He's been a science reporter for over a decade and it turns out that all the sequestion

is down to a disagreement over a tiny strip of paper.

Natural flow tests or LFTs for short, they're meant to tell you whether you have coronavirus.

They take less than half an hour much faster than the more familiar test, which is known

as a PCR test.

But there's the kind of tests we're all been used to for COVID for the last many months

now, which is a PCR polymerase chain reaction test and that takes a tiny piece of the viral

DNA and magnifies it and is incredibly good at spotting tiny, tiny amounts of it.

But the trouble is because it's so sensitive, even after your body has had the virus, killed

the virus and the virus has just sort of ruined and floating around in your bloodstream for

weeks afterwards, it will still detect it.

Your infectious for about four days, something like that and this will give you a positive

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