Valuing ResApp Health, page-271

You’re over-thinking this one @Phantom1.

ResApp-Dx only claims to distinguish between COVID-19 and an alternative respiratory disease such as pneumonia, which the preliminary trial shows it can. It doesn’t need to determine which form of pneumonia for the same reason that it doesn’t need to distinguish which form of COVID-19 it has detected.

This includes not needing to distinguish between viral pneumonia and bacterial pneumonia. Its purpose is not to be a replacement for a pathology lab.

Of relevance is the fact that neither ResApp-Dx nor the intended COVID screening device is designed to detect the presence of the SARS-CoV-2 virus. They will only detect COVID-19. COVID-19 is the respiratory infection that may or may not develop from being infected with viral SARS-CoV-2.

A positive RAP cough signature indicates the existence of COVID-19 whereas a PCR test indicates the presence of SARS-CoV-2. The body’s immune system eliminates the virus in 1-2 weeks but COVID-19 can still persist after that, even to the point of becoming LongCovid.

This distinction can explain the apparently low 80% specificity value in the preliminary trial. For 80% of the time RAP detects COVID-19 while the virus is still present, as shown by the PCR test. The remaining 20% of the time it detects the persistence of COVID-19 after the SARS-CoV-2 virus has been already eliminated by the immune system and PCR therefore is negative.

The 20% figure then would be a false positive for SARS-CoV-2 but a true positive for COVID-19.