(04-05-2021, 05:24 PM)TETLEY74 Wrote: Everybody seems obsessed with false positives with these tests ,the other side of the coin is how many false negatives are there too, id be more worried about them.
False negatives are generally not an issue as the tests are designed on the basis of having high sensitivities primarily, and high specificities secondarily coupled with the fact that the vast majority of people don't have COVID at any given time.
For example, currently in the population its estimated around 0.27% had COVID last week. With the sensitivity and specificity of the current NHS testing system which could be around 99% sensitivity and 97% specificity (it's a conservative estimate, the government claims it's higher than this but I really don't think so), if we test a RANDOM sample of 100000 people, nearly 3000 will give false positive results.
By contrast, an estimated 3 people out of 100000 will give false negative results.
The above also highlights why mass testing just isn't a good idea. The false positive rate isn't as high when you're testing symptomatic patients, which is why all the cries of "BUT WHAT ABOUT THE FALSE POSITIVES" hasn't really been that valid for the past year, however it's about to become more valid if they decide that we're going to be repeatedly testing the whole UK for COVID regardless of symptom status.