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Lead-time bias — USMLE Step 3 MCQ

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HardPreventive Medicine, Epidemiology, BiostatisticsLead-time biasUSMLE Step 3

A cancer screening program reports that 5-year survival improved after screening was introduced, but disease-specific mortality in the population did not change. The average time from diagnosis to death appears longer because cancers are found earlier. Which of the following is the most likely diagnosis?

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Correct answer: A — Lead-time bias

Lead-time bias occurs when earlier diagnosis increases measured survival time without delaying death.

Reference: USMLE Step 3 biostatistics and population health content outline: https://www.usmle.org/exam-resources/step-3-materials/step-3-content-outline-and-specifications