Impact of false-positives and false-negatives in the UK’s COVID-19 RT-PCR testing programmeCarl Mayers & Kate Baker, 3rd June 2020
Why are false positives a problem?DHSC figures [3] show that 100,664 tests were carried out on 31 May 2020 (Pillar 1 and 2 RT-PCR tests). 1,570 of those tests were positive for SARS-CoV-2 (1.6%). The majority of people tested on that day did not have SARS-CoV-2 (98.4% of tests are negative). When only a small proportion of people being tested have the virus, the operational false positive rate becomes very important. Clearly the false positive rate cannot exceed 1.6% on that day, and is likely to be much lower. If the operational false positive rate was 0.4%, 400 of the 1,570 positive tests would be false positives. That would represent 400 people being isolated when they are well, and much wasted effort in contact tracing. It is possible that a proportion of infections that we currently view as asymptomatic may in fact be due to these false positives.Unless we understand the operational false positive rate of the UK’s RT-PCR testing system we risk overestimating the COVID-19 incidence, the demand on track and trace, and the extent of asymptomatic infection.What causes false negatives?•Poor sampling technique. Nasopharyngeal sampling is invasive and can feel unpleasant. It may be less effective when carried out unsupervised, so the false negative rate may increase as sampling at home becomes more common.•Sample degradation. Samples may degrade when stored or while being transported.•Sampling too early. Viral shedding from individuals peaks just before, or at the onset of symptoms [4,5]. If samples are taken early in infection (1-4 days after infection) they have an increased false negative rate.•Sampling too late. Viral shedding declines after symptoms have peaked [6]. Samples taken at this stage of infection will show an increased false negative rate.
Now here is the point
If you do more testing a day like we doing mass testing, you will get more false-positives which then increases the overall numbers of new cases to higher levels than before to somwhat scary levels. This test is not fit for purpose because it cannot tell the difference between those infected and have live virus and can spread it from those with dead rna and who are not infectious. soo if you increase the daily figure to 500k tests then 2000 cases would be false positives, test 1million a day and then thats 4000 false positives.
So it give you a picture that is very untrue and pretty much what Mike Yeadon – Expert on Viruses says and more in this video https://youtu.be/8bX-wFVBP94 well worth a watch imo.