Theory 22/Sensitivity vs Specificity/Screening
Thresholds Buy One With the Other
The claim
Any screening threshold trades sensitivity against specificity, so the optimum is set by the relative cost of misses and false alarms rather than by test quality.
01Mechanism
Moving the threshold trades true positives for false positives; the balance is a cost ratio, not a property of the assay.
02Prediction
Optimal thresholds should shift with cost ratios.
03Refutation
Thresholds independent of costs would remove the optimisation.