Lead-time bias in cancer screening studies results in:
- A Overestimation of survival time due to earlier diagnosis without true change in outcome ✓
- B Preferential detection of slow-growing tumors by screening
- C Healthy participants being overrepresented in screening programs
- D Differences in survival due to variability in symptom severity
Correct answer: A. Overestimation of survival time due to earlier diagnosis without true change in outcome
Explanation
Lead-time bias occurs when screening advances the diagnosis to an earlier stage without changing the actual time of death. Apparent survival time is prolonged because the 'clock' starts earlier (at diagnosis), giving the illusion of improved survival even if the natural history and death date are unchanged. Length-biased sampling (option B) refers to preferential detection of slow-growing tumors; option C describes healthy worker/volunteer bias.
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.