A cross-sectional survey finds a high prevalence of rheumatoid arthritis (RA) among users of a specific herbal supplement compared to non-users. A researcher concludes the supplement causes RA. The MOST important flaw in this inference is:
- A Inability to establish temporal relationship between exposure and disease ✓
- B Berkson's bias from hospital-based sampling
- C Measurement error in disease diagnosis
- D Volunteer bias in participant selection
Correct answer: A. Inability to establish temporal relationship between exposure and disease
Explanation
Cross-sectional studies measure exposure and outcome simultaneously, making it impossible to determine whether the supplement use preceded or followed the RA diagnosis. This violates the criterion of temporality essential for causal inference. It is equally plausible that RA patients take the supplement as a remedy. This is the fundamental limitation of cross-sectional designs for establishing causation, not merely confounding or selection bias.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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