Lead time bias in cancer screening trials artificially inflates apparent survival time from diagnosis. The BEST study design to minimize lead time bias when evaluating a screening programme is:

• A Comparing disease-specific mortality rates between screened and unscreened populations in an RCT ✓
• B Measuring case-fatality rate from time of diagnosis
• C Using 5-year survival from diagnosis as the primary endpoint
• D Comparing incidence rates between screened and unscreened groups

Explanation

Lead time bias occurs because screening advances the date of diagnosis, making survival from diagnosis appear longer even if death occurs at the same time. Using disease-specific mortality rates in a randomized trial is the gold standard because it measures the actual goal — whether screening prevents deaths — regardless of when diagnosis was made. Survival from diagnosis (5-year survival) is severely affected by lead time. Incidence comparison is used for length bias, not lead time bias.

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

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Written and medically reviewed by the StethoPrep medical team.