Thread by @deeksj

For the sake of clear Public Health messages, listening to this interview on @theJeremyVine I'm tweeting some responses to the claims made by Peto

#1 "the lateral flow test has the remarkable ability of only picking up people who are likely to be infectious, or other words a danger to others."

It doesn't just pick out ONLY infectious people
It doesn't pick out ALL infectious people
Linkage to infectiousness is unclear.

It can only gives +ve results when viral loads are high (a limitation not an ability). Studies show viable virus in many people with low viral loads.

#2 "So if you want to know where you are a danger to others the lateral flow test is quite good"

OK if it is positive (provided we are not on rock bottom prevalence).

But there is a danger this comment will have been heard as:

"If negative you are not a danger, which THEY DO NOT".

#3 "If you want to know whether what you had a week or two ago was Covid then the PCR test is good. "

REALLY? Can't believe that this comment was really meant to come out this way!

The PCR is brilliant at detecting live virus before and during infection. Anybody with symptoms must get one.

I seriously hope nobody takes this as a suggestion you shouldn't get tested ASAP.

#4 "VINE: It is looking for people who are exuding the virus right now, is that right?
PETO: Yes. It’s a here-and-now are you infectious today test. "

Please, lets calm down the claims about infectiousness. The evidence is not there.

It tells you if you have high levels of virus, because that is all it can do.

Viable virus is more common in those with high levels, but is still there in some which are missed (see #1)

#5 "We can’t wait five years to get all the results perfectly before we roll it out"

In the past months studies would have taken weeks not years.

The Bham Uni study of 7000 took 2 weeks, school studies could have been done as fast.

We ONLY have data on IFT in 78 symptom free people with Covid and no children

No excuse for not doing the studies we now need

#6 I think the people there are pessimists who are perpetually the enemy of the good, this is a good test, but it is not perfect, no test is perfect, no one is claiming that it is.

People want good enough studies,

not perfect studies,

but definitely not bad studies or no studies.

#7 "Ok if you are in a school or place of work there well be [inaudible] to protect others in schools or places of work and it might be quite helpful for everybody else to know people are tested before they go to work."

It is wrong to suggest the tests should make others feel safe.

This is false reassurance given the test misses more than 60% of cases in L'pool and 33% with high viral loads.

Plenty of outbreak studies now show how this is misleading and dangerous

#8 "if you are home alone and you are anxious to know whether you are infectious for whatever reason it is a really nice test to have to decide whether you are infectious or not and that will help you a lot."

I guess if it makes you feel better and you are going to stay at home, nobody will get hurt. Sort of placebo effect?

But again overstating claims about this test saying your ARE or ARE NOT infectious.

It CANNOT do this

Particularly the ARE NOT infectious bit.

@threadmaker unroll

The ‘remarkable ability’ is a bit like a secondhand car salesman telling you the fact the car doesn’t have any wheels is fantastic as it means you will never get a puncture. Promoting a failure as an ability.