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Lead-time bias — USMLE Step 3 MCQ

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ModeratePreventive Medicine, Epidemiology, BiostatisticsLead-time biasUSMLE Step 3

A new cancer screening test detects disease 2 years earlier than usual, but the age at death is unchanged. Survival measured from diagnosis appears longer in the screened group. Which of the following is the most appropriate at this time?

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Correct answer: A — Recognize lead-time bias

Earlier diagnosis can increase measured survival time without delaying death, which is lead-time bias.

Reference: USPSTF methods; CDC epidemiology and biostatistics principles