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Lots of talk about false positives with LFDs but remember that during the first week of secondary schools using LFDs (in supervised testing) there were only 1,805 positives out of 3,867,007 tests. That's a positive rate of around 0.05% and the false positive rate cannot be greater than the positive rate, so chances of a false positive test with a LFD is very small.
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Good chart showing fewer hospitalisations per case. (on the correct y scale)
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The only thing I can't get my head around is how if she had a runny nose because those were her visible first symptoms of covid, how her snot did not contain enough virus to show up.
Early on in an infection you can have the virus in your body in low quantities but enough that your body mounts its immune response and you start to display symptoms such as fever/chills/sore throat/runny nose/cough, etc but it hasn't got to the point where the viral load is so much that it's spilling out of your mouth/nose in such quantities that could pose a problem for others nearby.
All the time after you're infected your immune response will be ramping up but, at the same time, the virus is replicating within your body. How serious the symptoms and damage are depend on how well and how swiftly the immune response starts to get the infection under control.
Lateral Flow isn't a test for being infected - that's a PCR test.
Lateral Flow is a test for being infectious - i.e. producing enough viral load to possibly infect others, and it's far from perfectAs the Government Guidance states, if you have symptoms then you shouldn't be doing a Lateral Flow test, you should go straight for a PCR.
And, as jellybaby says, the window for infectiousness (and tripping a lateral flow test) is a relatively short period (just a few days) of the overall infection window (a few weeks).
Once your body gets on top of the infection and your immune response has ramped up you may still display some/many of the symptoms (as above) but may stop producing enough virus out of your mouth/nose as to no longer be actively infectious and a danger to others. A lateral flow at test at this stage may return a negative but a PCR test should still return a positive.
LFDs are primarily to pick up on asymptomatic infections, because there isn't enough lab capacity to do PCR tests on everyone all the time. In an ideal world anyone/everyone could do a PCR test whenever they want, and get a result in a nice short time span.
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Good chart showing fewer hospitalisations per case. (on the correct y scale)
It's good but it's still concerning, especially given the percentage of people who've had one or both jabs.
The numbers and the anecdotal evidence of interviews with NHS staff show that instead of the ICU wards being inundated with Covid patients they're still seeing a lot of patients coming in, and it's the general respiratory wards that are filling up.
Compared to the previous peaks there are fewer patients coming in, and fewer serious cases, and average patient stay in hospital is lower, but there's still a growing number of people coming in and requiring hospital treatment. And it's growth that is the concern.
https://coronavirus.data.gov.uk/details/healthcare
We're back up to 300 people on mechanical ventilation up from the recent low of ~120 in mid-May. (The peak in late Jan was ~4,000.)
The other way to read this is that the first two waves killed off a lot of the most vulnerable people, and now the more transmissible and more virulent strains are going to give people serious enough doses to get them into hospital but without killing anywhere near as many. The question is what is the long term outcome for these people that are being saved from death?
Getting death figures down is obviously a good thing, but death figures alone do not show the full picture. We could get the death figures right down, but instead of hundreds of people dying each day we may end up with hundreds of people with life changing complications from serious Covid-19 infections each day instead.
The "patients in hospital" and "patients in mechanical ventilation beds" will be the figures to watch over the next few weeks/months.
On a more positive note (as I realise the above is a bit doom and gloom) but the vaccination program will reduce the number of deaths, and hopefully also the number of patients being admitted to hospital, and also reduce the average length of stay in hospital, and the average effect on the health of each individual patient (which is hard to measure directly).
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When I say the chart is "good" I only meant the chart itself. To members of the Log Scale Society this is a great example of why linear y scales are evil.
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Technically we are only advised to get a PCR test if we have:
a high temperature
a new, continuous cough
you’ve lost your sense of smell or taste or it’s changedSo, if you were following government guidance, you'd still be none the wiser.
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^ Seems mental that those are still the conditions for being eligible for a PCR test.
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Good point. Those thresholds were triggered the next day (high temperature) and this morning (cough + sense of taste gone). It's all happening at scrabble towers today!
Weirdest thing is having spent 18 months trying to avoid this virus I now have a grizzly 6 year old coughing it round the whole house. Ideally we'd isolate somewhat into different rooms, but in a two up two down semi with a patio garden and one bathroom between the fours of us- this is impossible.
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Weirdest thing is having spent 18 months trying to avoid this virus I now have a grizzly 6 year old coughing it round the whole house. Ideally we'd isolate somewhat into different rooms, but in a two up two down semi with a patio garden and one bathroom between the fours of us- this is impossible.
For what its worth, I feel for your situation! I'd be pretty miserable about having to self isolate as a household of two in a 2 bed flat. Not having kids to worry about has made this pandemic significantly easier for us.
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You can still get a PCR test if you want one
This is true.
there are walk in centers that don't require that criteria.
This is not true. They might not ask every visitor but that just means they aren't checking rather that it not being a requirement.
Edit: For clarity I mean that formally, all PCR test sites are instructed to ask about symptoms. Some do, some do not.
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A reminder that the FDA in USA said this of the Innova LFT as used in the UK
"In a scathing review, the US health agency suggested the performance of the test had not been established, presenting a risk to health, and that the tests should be thrown in the bin or returned to the California-based manufacturer Innova."
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I like to think of lateral flows as either positive or not positive (rather than negative) - I think saying they’re negative gives way too much reassurance/equivalence to a negative PCR which is a much more robust result. Lateral flows are basically good at picking up asymptomatic people with high viral load if used widely in the community, and screening clinically suspicious patients in hospital when other rapid tests are hard to come by, as a positive LFT is pretty likely to represent Covid.
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This paragraph stands out in particular.
But data suggests that the test performs worse in the real world. Liverpool was the first city to pilot the test for mass testing of people without symptoms – about 125,000 residents took the tests between 6 November and 9 December. Of those, 897 people who did not know they had the virus tested positive. However, tests in the field missed 60% of infections in people who were self-swabbing.
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Lateral flows are basically good at picking up asymptomatic people with high viral load if used widely in the community
Theoretically, correct.
However, Innova (who unless things have changed since the 10th June supply the LFD's), are impressively ineffective:
https://www.fda.gov/medical-devices/safety-communications/stop-using-innova-medical-group-sars-cov-2-antigen-rapid-qualitative-test-fda-safety-communication
https://blogs.bmj.com/bmj/2021/06/17/daily-contact-testing-trials-in-schools-are-unethical-and-extending-them-to-include-the-delta-variant-puts-everyone-at-risk/You also hit the key point earlier on- namely- a negative LFD + symptoms suggestive should still warrant a formal PCR test, but usually don't.
At which point their role becomes tenuous. -
At which point their role becomes tenuous.
In isolation yes.
But LFDs need to be considered within the scope of limited (and decreasing) PCR test capacity:-
https://twitter.com/chrischirp/status/1411753644404453380
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Test return times are getting longer in England (test and trace report & comparing specimen to report dates).A lot of testing capacity was closed in the spring in the expectation cases would never get that high again. They will (as govt admits!) - what's the plan? No testing?
"If we had proper PCR capacity to provide swift turnarounds (overnight ideally) then we wouldn't need to rely on LFDs to botch a countrywide testing strategy.
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No more masks indoors from 19th.
I'm going to get a better mask.
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Chat about Novel Coronavirus - 2019-nCoV - COVID-19
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Aren't the instructions blow your nose before so that no snot gets on the swab?