Read on Twitter
Mass testing. Results from the Liverpool trial. A thread. And a big problem.
https://www.gov.uk/government/publications/community-testing-explainer/community-testing-a-guide-for-local-delivery
https://www.gov.uk/government/publications/community-testing-explainer/community-testing-a-guide-for-local-delivery
A bit of background. To get out of national Lockdown 1, we were promised a test trace and isolate system. That uses PCR tests. These are accurate, but take time to get results back. There were also significant issues in the way that the Government organized 'NHS' Test & Trace
The Government is now relying on a less accurate technology, Lateral Flow tests. In order to roll these out nationally, the Government tested these.
In October, the first test was to see if they 'passed'.
They did, but we weren't told what this meant. https://twitter.com/Dr_D_Robertson/status/1323992106726281217
They did, but we weren't told what this meant. https://twitter.com/Dr_D_Robertson/status/1323992106726281217
So, more detailed results were published here https://twitter.com/Dr_D_Robertson/status/1326561351985229824
Which showed
"It has an overall sensitivity of 76.8% for all PCR positive individuals but detects over 95% of individuals with high viral loads" https://twitter.com/Dr_D_Robertson/status/1326561356833755136
"It has an overall sensitivity of 76.8% for all PCR positive individuals but detects over 95% of individuals with high viral loads" https://twitter.com/Dr_D_Robertson/status/1326561356833755136
But these were from ideal situations. What about when they are used in the field? That's where the Liverpool pilot came in.
And we now have results from that Liverpool pilot here: https://www.gov.uk/government/publications/community-testing-explainer/community-testing-a-guide-for-local-delivery
In the Liverpool trial, only *5 out of 10* cases were detected (and *7 out of 10* cases with 'higher' viral loads).
Not the same as the 76.8% and 95% from ideal conditions. Very far from it.
Not the same as the 76.8% and 95% from ideal conditions. Very far from it.
So... we have a mass testing regime that has large numbers of false negatives.
The problem with this is that people may take tests, be told the test is negative, and then *believe* they are negative.
The problem with this is that people may take tests, be told the test is negative, and then *believe* they are negative.
This can put vulnerable people at risk, and those in the communities in which they reside, such as residents in care homes.
The vital message is - if you have a negative test *IT DOES NOT MEAN YOU ARE NOT INFECTIOUS OR WILL NOT BE INEFECTIOUS*
The vital message is - if you have a negative test *IT DOES NOT MEAN YOU ARE NOT INFECTIOUS OR WILL NOT BE INEFECTIOUS*
And this is why the risk of Covid entering care homes is so great - although important to say LFD testing may not be relevant in this particular case. https://twitter.com/Davyshanks/status/1334529826619842565
There are two critical points:
1. Not enabling changes of behaviour at the same time eg promoting more visits or more visitors to care homes
2. Messaging for negative results - eg see this from university LFD testing from a couple of weeks ago https://twitter.com/Dr_D_Robertson/status/1330788873501290496?s=19
1. Not enabling changes of behaviour at the same time eg promoting more visits or more visitors to care homes
2. Messaging for negative results - eg see this from university LFD testing from a couple of weeks ago https://twitter.com/Dr_D_Robertson/status/1330788873501290496?s=19
