How well is the Innova test working in Liverpool?

This is a speculative calculation informed by data available from Liverpool. The source is the Liverpool mayor - reported 23,170 tests done, with 0.7% positive (so about 162) here. https://www.liverpoolecho.co.uk/news/liverpool-news/mayor-joe-anderson-gives-liverpool-19250704

Presume specificity 99.6%

No sensitivity data for this test - @UKPHE has data but not public

I estimate sensitivity of 75% based on independent evaluations done for WHO of other similar LFIA tests (range from 50% to 90%) - but in symptomatic patients https://www.finddx.org/covid-19/sarscov2-eval-antigen/

Using a prevalence of 400 per 100,000 you get the following 2x2 table:

11 of every 20 people told to isolate will not have Covid.

25 of every 100 people with Covid-19 will have negative results **** (I really hope they don’t now go and visit their granny)

One Covid case will have been found for every 330 tested.

**** Remember the sensitivity is a big guess – I’ve heard @PHE_uk have done studies in asymptomatic people- it is a scandal that they are not shared.

Real concern that Boris says we can use this for test-and-release – the -ve likelihood ratio is 0.25 - has Boris met Bayes?