A researcher wants to study the association between serum vitamin D levels measured during routine annual health checks and subsequent development of type 2 diabetes. He uses stored baseline samples from an existing cohort of 20,000 employees, identifies all incident diabetic cases after five years, and selects a random sample of non-diabetic employees for comparison. The design he has used is:

• A Nested case-control study ✓
• B Prospective cohort study
• C Case-cohort study
• D Retrospective cohort study

Explanation

B nested case-control study is a case-control study conducted entirely within an identified cohort: cases arising during follow-up are compared with controls sampled from those who remained free of disease. Its key strength is that exposure measurements predate outcome and are free of recall bias, while cost is far lower than analysing the whole cohort. In a case-cohort study controls are sampled from the full cohort at baseline regardless of later outcome, and full cohort designs would require measuring every participant.

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.