The odds ratio obtained from a case-control study provides a good approximation of the relative risk when:
- A The disease is rare in the population from which cases arose ✓
- B Controls are selected from hospital inpatients
- C The exposure prevalence exceeds 50 percent
- D Matching has been used in the design
Correct answer: A. The disease is rare in the population from which cases arose
Explanation
When disease incidence is low (commonly taken as less than 5 to 10 percent), the odds of disease approximate the probability of disease, so the exposure odds ratio closely estimates the relative risk. Hospital-based controls and matching affect selection and efficiency, not this approximation, and high exposure prevalence actually widens the gap between OR and RR for common outcomes.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.