When it comes to Covid testing the government has consistently over-promised and under-delivered.
That’s not to say its testing programme has been a flop. It rightly boasts it is carrying out more tests per day than practically any other country on Earth.
It’s also true that testing has given us a birds-eye view of the UK outbreak that we completely lacked during the first wave.
But the logistical failures of the test and trace system and the glacial pace of bringing the new “moonshot” tests online has made many people reluctant to take the government at its word. The plan to test the entire population of Liverpool should allow us to hold them to it.
It’s not started well. It emerged on Thursday night that one of the new tests due to be used in Liverpool, the saliva-based OptiGene Direct RT-Lamp test, only managed to detect 47% of positive cases in an earlier trial in Salford. That trial was radically scaled back last month, it’s understood due to problems with the saliva-based test.
Community testing in Liverpool will go ahead using another new “moonshot” test, a “lateral flow” test made in China by US company Innova. Lateral flow is the technology behind pregnancy test kits. Simple to use and read.
But the true reliability of these tests isn’t known, and the government has yet to publish any data on the months of testing it has done. But what we do know is that the test won't be run using saliva, making it slower with trained personnel required to carry out nose and throat swabs instead.
And there are still concerns about the lateral flow test’s real-world accuracy. Studies have shown they work on people with Covid symptoms, but it's not clear if they can detect virus in pre-symptomatic or asymptomatic people — which is the whole point of the Liverpool trial. And again, the data the government has got, hasn’t been published.
Now the pilot in Liverpool should be able to answer these questions if it’s done right.
For instance, will people tested with the lateral flow test be tested again using a “gold-standard” PCR test to check the new tests are accurate?
But given the pace at which it’s been set up there are concerns about that too. I understand that the team of scientists from various Liverpool Universities that are responsible for making the experiment work were only told it was happening on Monday - giving them three working days to prepare.
Friday’s roll-out of mass testing in Liverpool has the potential to stamp-out Covid. But don’t let images of the army testing thousands convince you we’re putting the boot in yet.
It’s a work in progress, and it might take some time.
Liverpool: The tests
Real-Time Polymerase Chain Reaction RT-PCR
The “gold standard”.
These tests rely on a throat or nose swab to get a sample of virus if present.
In a lab, RNA from the virus is tuned into DNA, which is then amplified to levels which it can be detected using enzymes and temperature cycles. The whole process takes a couple of hours.
Loop-mediated Isothermal Amplification (LAMP)
Can work using saliva or throat/nose swab.
A lab is still needed to extract the RNA from the virus and convert it to DNA but the amplification process is faster which means more tests can be turned around faster.
A sample — ideally saliva for speed and ease — is applied to a strip of blotting paper-like substrate that’s been impregnated with synthetic antibodies that bind to the virus.
Flowing along the substrate they then bind to other antibodies which change colour, giving an easy-to-read result if the virus is present.