RE: interesting1 Jun 2020 21:27
Evening David, just to provide the full illustration of why our test has been condemned as apparently useless. You can then make your own mind up. Using the exact example given.
If there was a population of 100,000 then 270 would have Covid = the prevalence of 0.27%. Of these, all 270 would be found as positive as it is 100% sensitive. That leaves 99,730. Of these, we would get 200 false positives using a specificity of 99.8%. This equates to the positive predictive value of 57% as stated = 270/(270+200).
My view. The suggestion that isolating an additional 200 people out of 100,000 would render a test useless, whilst capturing every true positive, is complete and utter nonsense.