The PCR test is reliable and effective. Like any diagnostic test however, there is always the small possibility of a false negative or a false positive result. blah, blah
Full response here. Woefully inadequate, in my opinion.
The ONS current estimate of prevalence is 1.18% here
The latest daily data here shows 60,916 'cases' in 72,190+378,918 PCR tests, or 13.50%. On a 7-day average, 'cases'/PCR tests = 13.28%.
Tested 'cases' divided by prevalence is thus 13.28/1.18 = 11.25 times as many as one would expect for the real prevalence on a large test population that approaches the distribution in the wider population. Remember that this test population has uncontrolled symptom checks - symptoms that also have non-covid causes.
If this were to translate directly into specificity, one would get 93.2% and the percentage of false positives would be 93%. That is a true:false ratio of 1:13.7. Hardly a "small possibility."
Furthermore, as we all know, these 'cases' are not necessarily true 'cases' and not necessarily infectious. And if they were true cases, they are shooting up at a far greater rate than the real cases that require hospitalisation. So the more the better, because it shows resistance to the virus. As such, these high 'case' numbers should be used by the government to reduce fear rather than increase it.
following the link to the full response leads to this Assurance of SARS-CoV-2 RNA positive results during periods of low prevalence
Updated 16 October 2020
which has this diagram
Positive test results at the limit of detection that occur late in the cycle of infection represent individuals with a low or very low risk of transmission, as a result of the decline in infectious virus production or remnants of viral RNA in respiratory secretions.
which will be True Positives and counted as cases.
Yes - I got this and was depressed and disappointed by the complacency of the communication. Especially disgusted by the unapologetic admission that there was no mechanism for measuring the problem.
They might just as well have said 'shut up and do as you are told'.
Still - didn't hurt to register interest in the accuracy of the test.
Latest published prevalence rate of 1.18% was on 24 Dec, relating to the week finishing 1 week before that. These are based on a sample of the population.
PCR result @ 60,916 cases on 4 Jan (published on 5 Jan) and are dominated by people with some concern over symptoms.
Both time and sampling method are incompatible.
Hence these numbers cannot be combined to draw conclusions on test accuracy.
Put simply, people who have symptoms are much more likely to test positive, than a random sample of people.
Put simply, people who have symptoms are much more likely to test positive, than a random sample of people.
Which is why you're supposed to have symptoms to be allowed to book and go for a pillar 2 test.
