A case-control study is conducted to evaluate the association between pesticide exposure and non-Hodgkin lymphoma. Controls are selected from the same hospitals where cases are admitted. The odds ratio is estimated as 3.4. Which specific bias is MOST likely to have inflated this estimate?

• A Neyman's bias
• B Recall bias
• C Berkson's bias ✓
• D Hawthorne effect

Explanation

Berkson's bias (hospital admission rate bias) occurs when hospital controls are used; hospitalized patients often have conditions that share risk factors with the exposure under study, artificially inflating or deflating the observed odds ratio. Neyman's (prevalence-incidence) bias affects diseases with high case fatality before hospital admission. Recall bias affects self-reported exposures but would affect cases more than controls. Hawthorne effect alters behaviour, not recall.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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