Work out false discovery rate in screening instantly with clear inputs, formula shown and shareable results.
Applies Bayes' theorem to prevalence, sensitivity and specificity to show what share of positive screening results are false.
Predictive values
PPV = prevalence x sensitivity / (prevalence x sensitivity + (1 - prevalence) x (1 - specificity)); false discovery rate = 1 - PPV
Even a small false positive rate applied to the large healthy majority produces more false than true positives.
Two-stage screening: a sensitive first test followed by a highly specific confirmatory test.