Understanding sensitivity and specificity with the right side of the brain

Others have already highlighted the BMJ Editor's repetition of
Loong's main error in asking the wrong question. However, I believe there
is an answer to the question as asked, to "explain why a test with 95%
sensitivity might identify only 1% of affected people in the general
population?" Surely the answer to this conundrum is that about 99% of
those affected were not tested!

Tze-Wey Loong's final point is disingenuous. To demonstrate a
sensitivity of 99.999%, one would need to test 100,000 individuals with
the disease to yield a single false negative result. With a disease
prevalence of 0.033%, this would require a population of 303,030,303 to
find 100,000 affected individuals in whom to test the test.

Competing interests:  
None declared