Within an ongoing cohort of 10,000 adults with stored serum samples, investigators identify all participants who later developed type 2 diabetes and select a sample of non-diabetic participants matched to each case on calendar time of diagnosis. They then assay a costly inflammatory marker in both groups using banked serum. This design is best described as a:

• A Retrospective cohort study
• B Nested case-control study ✓
• C Case-crossover study
• D Historical prospective study with full follow-up

Explanation

B nested (embedded) case-control study is conducted entirely within a defined cohort: incident cases arising during follow-up are compared with controls sampled from cohort members still at risk when each case occurs. Exposure is measured from specimens collected before disease onset, giving temporality like a cohort while costing far less than assaying the whole cohort. B retrospective cohort would require measuring exposure in every member, defeating the purpose of sampling.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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