A researcher conducts a case-control study on pesticide exposure and non-Hodgkin lymphoma. Cases are recruited from cancer hospital registries (which over-represent advanced cases), while controls are selected from the same hospital with other diagnoses. Which combination of biases is MOST likely operating?
- A Neyman bias + Berkson bias ✓
- B Recall bias + Hawthorne effect
- C Lead-time bias + Length-biased sampling
- D Interviewer bias + Performance bias
Correct answer: A. Neyman bias + Berkson bias
Explanation
Neyman (prevalence-incidence) bias occurs when cases recruited from hospital registries exclude early/fatal cases, distorting the exposure-disease association. Berkson bias (hospital admission rate bias) occurs when hospital-based controls are not representative of the base population from which cases arose, because hospitalised patients have different exposure profiles. Recall and Hawthorne biases do not explain the structural sampling distortions described.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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