A screening program detects prostate cancer 3 years earlier on average than clinical diagnosis. Five-year survival from time of diagnosis rises sharply, but age at death is unchanged. The inflated survival is best explained by:

• A Lead time bias ✓
• B Length bias sampling
• C Neyman's bias
• D Publication bias

Explanation

Screening shifts the date of diagnosis earlier without delaying death, so measured survival increases purely because observation starts sooner. This is lead time bias, the reason survival alone cannot prove screening benefit and randomized trials measuring mortality are required. Length bias is the overrepresentation of slow-growing indolent tumors in screened populations, Neyman's bias arises when prevalent rather than incident cases are studied, and publication bias concerns selective reporting of positive studies.

Reference: Gordis Epidemiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.