Lead-time bias in cancer screening trials gives a false impression of improved survival because:

• A Screened patients receive better treatment due to physician attention
• B Survival time from diagnosis is extended by early detection even if actual time of death is unchanged ✓
• C Slowly progressing cancers are preferentially detected on screening
• D Patients who participate in screening are healthier than those who don't

Explanation

Lead-time bias occurs because screening detects disease earlier in its natural history; even if the date of death is unchanged, survival time measured from diagnosis appears longer. This creates a false impression of benefit. Length-time bias (option C) refers to the preferential detection of slow-growing lesions by periodic screening. Healthy volunteer effect corresponds to option D. Both are different types of bias in screening evaluation.

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.