A district plans to screen for phenylketonuria in newborns. The disease is serious, early treatment completely prevents intellectual disability, and the confirmatory test is cheap and harmless. When choosing the cutoff value for the initial screening test, the programme should select a cutoff that:

• A Maximizes specificity to reduce unnecessary confirmatory testing
• B Maximizes positive predictive value in the population
• C Balances sensitivity and specificity equally at the ROC curve midpoint
• D Maximizes sensitivity even at the cost of more false positives ✓

Explanation

When the disease is severe but treatable, missing a case is catastrophic while a false positive costs only an inexpensive confirmatory test. The cutoff should therefore be shifted toward maximum sensitivity, accepting more false positives. Maximizing specificity suits situations where confirmation is costly or hazardous. Positive predictive value depends mainly on prevalence and cannot be maximized by cutoff choice alone in a low-prevalence newborn population.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.