A disease surveillance system classifies all hospital-admitted cases as 'confirmed'. When disease prevalence in the community is low (1%) but hospitalization is more common among severe cases, the calculated hospital-based prevalence will be:

• A Equal to community prevalence because hospitalization is random
• B Higher than true community prevalence due to ascertainment bias ✓
• C Lower due to healthy worker effect
• D Unaffected because hospital and community populations are independent

Explanation

Hospital-based surveillance over-represents severe or symptomatic cases because mild cases are never hospitalized; this is a form of ascertainment (detection) bias leading to prevalence overestimation. The healthy worker effect is an occupational epidemiology phenomenon. Hospitals are not independent samples of the community — they are enriched for diseased individuals, which is precisely Berkson's principle.

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.