Dear list members
Can anyone give advice for calculations regarding
specificity and sensitivity of a screening test? For
example, suppose that 1000 patients were screened. 200 were
tested positive and the remainder tested negative. Of the
200, 75 were found to be true positives and 125 were found
to be false positives. Of the 800 test negatives, a random
10% sample were further tested for the disease of whom 20
were found to be positive (ie false negatives) and 60 were
truly negative.
My question is: how do you calculate specificity and
sensitivity based on the fact that only 10% of the test
negatives were followed up?
All suggestions are appreciated.
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