I thought it would be wise to run the numbers that we have on student testing in England. In Scotland we know how many students are taking part, and so we can judge things like the overall participation rates of the student body. We also know how many tests are being carried out by provider, and (with some time lag) how many positive lateral flow tests are later confirmed by PCR test.
Naturally we don’t have that kind of information in England. We do though have totals for the number of LF tests being carried out within the higher education part of the programme, and how many of them are coming up positive.
Let’s focus on the pre-Christmas “get them home” exercise first. 319,567 tests were carried out in England. We don’t know how many of those were staff, so we’ll have to pretend for now they were all students.
We also don’t know how many students got tested twice – in Scotland before Christmas it was 90 per cent, and that remaining 10 per cent can’t all have been because test one of two was positive. So let’s run that number across and assume that the proportions were similar in England, which would suggest 175,762 students were tested – a participation rate of just under 10%. That suggests the sector has a major problem in persuading students to do this.
The English pre-Xmas LF tests exercise found 1,103 positives, a 0.35% positivity rate, which is interesting – Scotland had a 0.08% positivity rate. Bear in mind that all LF tests have false positives, which is worked out via confirmatory PCR testing. For Innova LF tests, the Department of Health and Social Care says about 3 per 1000 (0.3%) are false positives. In Scotland pre-Xmas it looks like it was 0.02% – 28.5% of those who tested LF positive went on to be found negative when PCR tested.
If we use the Scottish accuracy results on England’s numbers, that suggests that 314 of the students who tested positive before Xmas in England would have gone on to be confirmed negative by PCR – but we’ve not been given false positive / PCR confirmation figures by DHSC or DfE.
Now let’s look at what’s going on this term. The figures we have are complicated by the fact that we only introduced an “urge” to get tested twice a week last month. And England has now dropped confirmatory PCR tests following positive LFD tests, so we’ll now never get that data.
One question is – are students playing ball? Again we don’t know how many tests are students and we don’t know how many students are “at” their university town/city. But for example – between the 11th and 17th Feb, 50,659 tests were carried out in the English sector.
Let’s very generously assume all were students and students only got one test that week. That suggests only about 2.5% of students are “back” and in situ, which is significantly lower than almost everyone I speak to in the sector thinks.
In the first three weeks of February, 469 LF tests in higher education in England were positive. If we run the Scottish falsies rate across in the absence of other intel, that suggests that 134 of those students (or staff) have been self-isolating for no reason.
But running the Scottish “28.5% of positives end up negatives” rate may not be helpful as community prevalence falls.
To put this another way, DHSC says Innova LF tests have an overall FP rate of 0.3%. In the first three weeks of February, the positive rate in HE was 0.32%. In other words it’s now entirely possible that almost every single positive we found in English HE in those weeks in February were false positives.
And so as we ramp up “practical” student return on March 8th, we’ll likely be arm twisting students to take part, and in doing so will end up putting thousands of students (and staff) in isolation for no reason for 10 days – many over Easter. And there’s very little evidence that this is making any difference.
Given the vast costs (in cash, space, time and other capacity) to government and universities, and the risk both of false negatives (which encourage risk taking) and false positives (which generate unnecessary isolation), can someone remind me why on earth this exercise is still running as it is in universities – other than to serve a type of theatre?