/ Covid home testing - game changer?

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pasbury 25 Mar 2020

https://www.theguardian.com/world/2020/mar/25/uk-coronavirus-mass-home-testing-to-be-made-available-within-days

This seems like a positive development to me. I have several colleagues who 'think' they've had Covid19 but without a test you can't really use them as a data point.

However I can see that it would need to be carefully handled to avoid an 'I'm alright jack' behavioral response that would compromise the lockdown.

Neil Williams 25 Mar 2020
In reply to pasbury:

Ooh, good.  I would love to know if I've had it, I think I have.  Happy to pay the cost to save the NHS money.

Fozzy 25 Mar 2020
In reply to pasbury:

Good. I’m currently quarantined with a persistent dry cough, wheezy/out of breath, headaches & generally feeling crap. I’ve not, however, got a high temp. Being able to test & get a definite yes or no would be much appreciated before I head back into work after my 7 days in solitary. 

skog 25 Mar 2020
In reply to pasbury:

This looks like good news - but surely there would still have to be some sort of official, recorded test done before people could "get back to normal"? Something you could prove you'd had?

Otherwise, inevitably, quite a lot of people will just pretend they've tested and found themselves to have had it.

DancingOnRock 25 Mar 2020
In reply to skog:

Yes. The Government don’t seem to be so sure it’ll be ‘days’. They’re quite concerned about the accuracy. 

girlymonkey 25 Mar 2020
In reply to pasbury:

Do we know if these will show up the stage before the symptoms start, when you can be infectious? The article says the anti-bodies are produced early in the infection, but how early?

How do we deal with some people coming out of lock down and others not? 

Looks like a good step if it is accurate, but I don't know if it solves the current lockdown crisis?

stevieb 25 Mar 2020
In reply to girlymonkey:

> Do we know if these will show up the stage before the symptoms start, when you can be infectious? The article says the anti-bodies are produced early in the infection, but how early?

I don’t know if it’s the same test kit, but one kit was claiming it could detect between 3-33 days after infection. Shorter and you wouldn’t have the antibodies, longer and they were no longer detectable. 

Archy Styrigg 25 Mar 2020
In reply to Neil Williams:

> Ooh, good.  I would love to know if I've had it, I think I have.  Happy to pay the cost to save the NHS money.


Is the race still on to be first confirmed UKCer to have had CV19?

1
girlymonkey 25 Mar 2020
In reply to stevieb:

Interesting, if they are not detectable after 33 days, does that mean they are not as prevalent? Not so effective? Are we saying we can be infected again? (I know nothing about this sort of stuff!)

stevieb 25 Mar 2020
In reply to girlymonkey:

> Interesting, if they are not detectable after 33 days, does that mean they are not as prevalent? Not so effective? Are we saying we can be infected again? (I know nothing about this sort of stuff!)

I don’t think so. I don’t know this stuff either, so I may be talking complete rubbish, but I think there is a difference between what your immune system ‘remembers’ and what can be traced. 

Neil Williams 25 Mar 2020
In reply to Archy Styrigg:

> Is the race still on to be first confirmed UKCer to have had CV19?

I think there are people who have had more conclusive symptoms than me.  Has anyone had the "normal" test?

Neil Williams 25 Mar 2020
In reply to girlymonkey:

> Interesting, if they are not detectable after 33 days, does that mean they are not as prevalent? Not so effective? Are we saying we can be infected again? (I know nothing about this sort of stuff!)

It doesn't necessarily mean you can be reinfected, using coeliac as an example you are coeliac for life, but the test doesn't work unless you've eaten at least two slices of bread a day for two months.  (While coeliac is an autoimmune condition, it's initially tested for by looking for antibodies in exactly the same way).

mik82 25 Mar 2020
In reply to Archy Styrigg:

There's definitely a few people on here that have had positive tests

pasbury 25 Mar 2020
In reply to girlymonkey:

Good question but I haven't a clue as I'm an aerospace engineer.

I do agree with your point that this does not, and should not, affect lockdown at all.

Post edited at 19:31
captain paranoia 25 Mar 2020
In reply to pasbury:

News at lunchtime said the tests would only be available for frontline health workers, not for the general public. They're only talking about buying 3.5 million.

Of course, things are moving very quickly...

Neil Williams 25 Mar 2020
In reply to captain paranoia:

> News at lunchtime said the tests would only be available for frontline health workers, not for the general public. They're only talking about buying 3.5 million.

> Of course, things are moving very quickly...

I would expect them to be available commercially soon enough.

Dave Garnett 25 Mar 2020
In reply to stevieb:

> I don’t know if it’s the same test kit, but one kit was claiming it could detect between 3-33 days after infection.

Wow, so much that is misleading and unclear in that Guardian article.  Not surprised you are confused.

They consistently mix up two completely different tests.  The one available now is a highly sensitive test detecting viral RNA by converting it to DNA and amplifying it (an RTqPCR TaqMan assay).  This should detect virus very early in the infection (theoretically it might detect a single molecule of viral RNA).  I don’t know how long it takes for the virus to be cleared completely but I can imagine that it might be negative a few weeks after clinical signs have disappeared (assuming there’s no remaining latent virus - not likely in this case).

The second test is an ‘antigen’ / ‘antibody’ / serological test.  This detects circulating specific antibodies against viral proteins.  For  a primary infection (where the person has never seen this particular virus) antibodies gradually rise over a couple of weeks and peak after about a month.  They then decline if there’s no further challenge but might still be detectable for some months with a good test.

Actually, for viral infections like this, a better measure might be antigen-specific CD8+ T cells, but I digress.

I think it’s this second test that the fuss about but don’t worry, because Chris Whitty made it very clear that, despite what Matt Hancock said, there was no way the general public would have access to serological tests any time soon.

Post edited at 20:21

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