COVID-19: MOBILE TESTING DAY 1

Oxford has a problem.  Daily infection rates have been rising at a disconcerting speed.  As of 21 August, the City was 17th highest in the country, after Oldham, Leicester and a few others.

The response has been to set up mobile testing stations in the car park behind my local Tesco's, for the next three days at least.  I was going to pop in to the shop anyway, so dropped by to have a chat with the staff proudly wearing their NHS Test and Trace weatheralls.

The folks from Serco had arrived in unmarked white vans, and set up several gazebos in the rain, with boxes of swab kits.  Swabs are then sent off to labs for processing.

The first thing they confirmed is that they are only doing "Got it" tests, not "Had it" antibody tests.  They want to find out what's going on with infections now, and get relevant people to isolate.  Presumably then follow up with tracing contacts.

The second thing is that the test involves self-swabbing with two swabs:

• 10 seconds tickling one's tonsils
• 10 seconds up the nose

The person I spoke to couldn't advise on false negative rates.  But false negatives have been known to be up to 30%, even when done by medical staff.  Could be higher if self-swabbing.  At least people tested here are supervised, whereas testing kits sent to people's homes are not supervised.


CONSEQUENCES

False Negatives

My concern about these tests, especially when self-swabbing, is that people with COVID-type symptoms could be released into the community as apparently uninfected.  Indeed the official guidance allows that, with a number of provisos.  This is discussed in more detail for Day 3, when I received the official Negative test result.


Accuracy of "New Confirmed Cases"

The official PHE statistics on testing for daily "New Confirmed Cases" from NHS Test and Trace are inherently understated:

• Not everyone eligible for a test gets it done
• False negatives, as above
• Asymptomatic people are not eligible to be tested.  They can be infectious.

At the country level, comparison of PHE statistics with those from other studies suggests that official figures need to be multiplied by around 5 to get a more realistic estimate of total daily infections.

Where local testing makes it easier for people to get tested, the multiplier would be expected to reduce.  The estimate is around 4 times the local figures.  Still significantly higher than the basic figures reported.

Furthermore, when consdering the number of peope out and about infectious, we should assume that not everyone who should self-isolate does so.


Interaction with National Testing

As set out here, a national testing programme at the scale that would be required would be ridiculous, both from practical and financial angles.

So the focus of testing must be these mobile teams visiting hotspots.   But the need for them must be the exception.  That can only be done if general rates are far lower than they are now.  As part of a #NearZero strategy.

Here are the updates for Day 2 and Day 3, when I got tested.