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On what dataset are you basing your 50% false positive estimate? Your article is a very thorough rundown of the many possible weaknesses of the testing approach but doesn't appear to have any analysis of actual test results to demonstrate that your concerns are actually valid in real-world conditions.
Tim, the Video is interesting, but the interviewer is part of the great US Conspiracy community. Everything that is said in the interview is true, but spun. She also ignores the fact that Primers have evolved as more about the virus genome is known and that the parts of the viral RNA being targeted are selected to ensure specificity. So the PCR test, as used today in the UK, is reasonably accurate in detecting Coronavirus RNA, but it is subject to so many possible sources of error that I believe it is reporting far to many false positives.
Specifically:
Sampling Error: sticking a swab up your nose in the hope of collecting viable viral particles is the first source of error: if trained medics do it then it is less prone to error. The test can be "gamed" by using a nasal spray before sampling to rinse the nose and back of the throat. Why would anyone do that? Because they feel OK and don't want to self isolate for 10 days, especially if they don't get paid.
Timing: Following infection viral load rises and falls, with peak shedding about a week after infection. Sampling too early or too late will cause an erroneous result.
Screening: People are getting tested almost at will: there is no proper review of symptoms and possible exposure. My position is that a positive PCR test should be followed up with a Lateral Flow test and a review of symptoms.
Viral Debris: The PCR test cannot differentiate between dead viral junk that is of no risk to anyone and live RNA. Going back to timing anyone who has had mild covid will test positive for several weeks after they are no longer infectious. It is also possible to pick up viral debris from the air, which is why face masks are important in places like a supermarket.
Cycle Time (CT) The video talks about cycle times of 45: in the UK 35 is used, but most Virologists believe anything more than 30 indicates the method is being abused to get a result. Cycle Times are not reported: anyone who tests positive and is asymptomatic should be told the CT number and if it is over 30 demand a lateral flow test and a clinical review. The lateral flow test is cheap, takes 30 minutes and looks at the proteins on the viral envelope, not the RNA.
Taken all together it is my professional opinion that upto 50% of reported COVID cases are false positives, but there are no real data to confirm my estimate or the ONS data. It could be 20%, it could be 50%. The only 100% certain way to confirm a PCR positive test is by using classical virology methods, these are expensive and take time.
Why does this matter? Because very important decisions are being made based on PCR Testing numbers that are unconfirmed by any other method. We have about 10,000 positive PCR tests a day. The impact of returning the kids to school is critical, if there is a surge then the Government MAY have to delay steps 2, 3 and 4. But it is also possible that there may be a surge but without any increase in hospitalisations or deaths. That all this depends on a method that is flawed is a concern.
