Lead time bias in cancer screening studies causes:
- A Apparent improvement in survival from diagnosis but not true extension of life ✓
- B Detection of less aggressive tumours that would never have caused death
- C Failure to detect early disease due to long pre-clinical phase
- D Over-representation of rapid-growing tumours in screen-detected cancers
Correct answer: A. Apparent improvement in survival from diagnosis but not true extension of life
Explanation
Lead time bias occurs because screening detects disease earlier (advancing the time of diagnosis), making patients appear to survive longer from diagnosis without actually living longer. Survival is measured from diagnosis, so it appears improved even if death occurs at the same time. Length time bias (option B) refers to detection of slower-growing tumours by screening.
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.