Lead-time bias in cancer screening occurs when a screened group appears to have a longer survival than an unscreened group. The most appropriate outcome measure to avoid lead-time bias when evaluating a screening programme is:

• A 5-year survival rate from time of diagnosis
• B Stage distribution at diagnosis in screened vs. unscreened populations
• C Median survival from time of diagnosis
• D Disease-specific mortality rate in screened vs. unscreened populations ✓

Explanation

Lead-time bias occurs because screening advances the time of diagnosis; patients appear to survive longer simply because they are diagnosed earlier, not because they live longer. Disease-specific mortality rate in screened versus unscreened populations is the most valid endpoint as it is independent of when diagnosis is made and measures whether screening actually prevents deaths. Survival rates from diagnosis are vulnerable to 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.