A study examining mobile phone use and glioma recruits cases from neurosurgery units and controls from orthopaedic wards with fractures — an exposure (phone use) completely unrelated to the control condition. Which type of validity concern is LEAST addressed by this design?

• A Berkson's bias from hospitalised controls
• B Recall bias among cases regarding past exposure ✓
• C Information bias from unblinded interviewers
• D Reverse causality

Explanation

Recall bias — differential recall of exposure between cases and controls — is a persistent threat in case-control studies and is not eliminated by the choice of hospital controls with an unrelated admission condition. Berkson's bias is partly addressed by choosing controls with an unrelated condition. Blinding interviewers addresses information bias. Reverse causality is intrinsically addressed by the retrospective design asking about past exposure before disease.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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