The most interesting figures I found from the presentation is the comparison of apparent results of our RAP test with those that would be obtained from the ‘Gold Standard’ PCR test.
My understanding of the maths using the figures in the presentation is -
Scenario 1 - The PCR Test :
You have 2,000 people* lined up at the test centre to get a PCR test and 100 (ie 5%) of them actually have Covid.
The PCR test is of 95% Sensitivity. As a result, of the 100 people who actually have Covid 95 of them are told they have Covid and 5 are told they have not.
Because the PCR test is 99.6% (lets say 100%) Specific all 95 people who were told they have Covid actually do have Covid and of the 1,905 people who were told they do not have Covid only the 5 above have been incorrectly diagnosed.
As a result, following the application of the ‘Gold Standard’ to 2,000 people, 5 people are wandering around the community thinking and acting as if they don’t have Covid when they actually do.
Scenario 2 - The RAP Test :
You have 2,000 people taking a RAP test whilst siting at home and 100 (ie 5%) of them actually have Covid.
The RAP test is of 92% Sensitivity. As a result, of the 100 people who actually have Covid 92 of them are told they have Covid and 8 are told they have not.
Because the RAP test is 80% Specific 20% of the people who don’t have Covid are given a false positive result. They then go on to have a PCR test - which is the alternative they would otherwise have been about to do anyway - and since this is 100% Specific these will all be now told, correctly, that they do not have Covid.
The end result is, with the RAP test 8 people wander around the community thinking and acting as if they don’t have Covid when they actually do, compared with 5 people doing exactly the same thing if the ‘Gold-Standard’ PCR test was undertaken instead by all 2,000 people.
Not totally as good, and I might be just a little bit biased, but if this is so that sounds pretty good to me.
This would certainly be a lot better than relying only on a RAT (Rapid Antigen) test which, according to the presentation figures, wrongly informs 20% - 40% of those people with Covid that they don’t have it. This would result in 20 to 40 Covid positive people wandering around the community.
I note from the presentation that the RAT test, like the PCR test, is 99.6% (ie 100%) Specific with respect to a positive result so it may be that the false positives sitting at home after doing the RAP test might only now have to continue to sit there and take one of their RAT tests they have purchased rather than proceed to the more complex PCR test.
Anyone read the figures differently?
poorinvestor
* I am using 2,000, not 1,000, so I don’t have to deal with half-people in the maths, with the result that everything here has been multiplied by 2 compared with the figures in the presentation.
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