Under which condition can the odds ratio from a case-control study be used as a direct estimate of relative risk?

• A When controls are selected from hospitalized patients only
• B When recall bias has been minimized
• C When matching has been performed on age and sex
• D When the disease under study is rare in the population ✓

Explanation

When disease frequency is low, generally below about 10 percent prevalence, the number of non-cases who develop disease during the study period is negligible, so odds of disease approximate risk and the odds ratio approximates relative risk. Hospital-based controls and matching affect selection and comparability but do not make the OR equal the RR, and minimizing recall bias improves validity without altering the mathematical approximation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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