A screening test for prostate cancer detects a higher proportion of slow-growing, indolent tumors than aggressive rapidly fatal ones. If screening effectiveness is judged only by the outcomes of screen-detected cases, the benefit will be overestimated. This phenomenon is known as:

• A Neyman's bias
• B Hawthorne effect
• C Healthy worker effect
• D Length bias ✓

Explanation

Length bias occurs because screening intervals allow slowly progressing, less lethal disease to remain detectable longer, while fast-progressing disease arises and kills between screens. Screen-detected cases are therefore enriched with better-prognosis tumors, inflating apparent benefit. Neyman's bias refers to exposure measurement after disease onset in prevalent cases, and the healthy worker effect is reduced mortality among employed populations, neither of which concerns tumor biology at detection.

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.