[set fair (OP)]

I'm talking about the ones where you spit and look at/for two lines akin to pregnancy tests. Although they have 50% false negatives it seems the 50% is not hit and miss, rather they are simply less sensitvie - can't detect a low viral load but don't miss a high load. Done daily they catch an infected person just before or just as they become infectious. Cost around £10 a week. Of course they're open to abuse eg person tests positive, one last shop before they isolate. A trial in hot spots looks like a good idea.

Well explained on Medcram

[alancalverd]

Of course they're open to abuse eg person tests positive,.......

Or negative, as they are 50% false negative.

Essentially you are looking for a needle in a haystack with a device that misses half the needles, knowing that the presence of a needle can be disastrous (which is why you are looking for it in the first place).

[set fair (OP)]

No, they will catch everyone, just not until about the third day after infection.

[alancalverd]

Two problems.
1. In the video. Dr Mina mentioned the rapid escalation of viral load in the early phase - several orders of magnitude "in hours". So a kid could happily test negative in the morning, go to school, and be shedding bucketloads of virus on the bus home.
2. The suggestion that people with Ct above about 35 are not infectious doesn't fit with UK clinical experience where patients were discharged "free from infection" from hospital and infected their care home.
 

[set fair (OP)]

2. The suggestion that people with Ct above about 35 are not infectious doesn't fit with UK clinical experience where patients were discharged "free from infection" from hospital and infected their care home.

Where's the evidence that this happened?

[alancalverd]

The evidence was presented to the Public Accounts Committee who published a couple of days ago

https://www.bbc.co.uk/news/uk-politics-53574265

Given the graphs of Ct against time, and the average length of hospital stay of those with COVID symptoms, it's quite likely that most of those discharged to care homes were indeed above 35.

[set fair (OP)]

That is not evidence. The home testing is suggested to catch people before they become infectious, after they have been diagnosed they would obviously need the usual 2 negative tests 24+ hours apart to be cleared.

I'm not saying this is going to solve everything but if it cut asymptomaic spread from 5 days to 1 day or from 10 days to half a day, then there is the potential to cut infection rates by 20-90%. I think its foolish not to try.

[alancalverd]

So you need a test that will distinguish Ct35 from Ct45, hence the needle in a haystack metaphor. I'm not sure that any home test has got that sensitivity.

[set fair (OP)]

Slovakia has already halved the number of cases using these tests.

[alancalverd]

Anything that stops people from mixing with others, will reduce the infection rate. Suppose we toss a coin (the equivalent to a 50% test of anything).

Heads, I have COVID so shouldn't mix with others in case I infect them.

Tails, I don't have COVID so shouldn't mix with others in case they infect me.

The great thing is that you can swap my penny test  for any COVID test, regardless of its accuracy, and improve outcomes.

It's a simplified triage problem. Around 1 - 2% of the population definitely have COVID, for which there is no treatment, so they should stay indoors until they cease to be infectious. Possibly 5% of the population have asymptomatic COVID (particularly schoolchildren) so they should stay indoors in case they are infectious. About 93% of the population are susceptible to COVID, so they should....er....stay indoors until everyone has quarantined.  If a bogus test reinforces the message, so much the better.