A researcher wants to study whether a specific genetic polymorphism predisposes to lymphoma using stored blood samples collected years ago from a large ongoing cohort. Cases developing lymphoma are identified, and for each case, controls are selected from cohort members who were under surveillance when the case was diagnosed. This design is best described as:

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

Explanation

B nested case-control study is embedded within a defined cohort: cases arise during follow-up, and controls are sampled from cohort members still at risk at the moment each case is diagnosed, preserving temporality. Exposure data predate disease, avoiding recall bias, at far lower cost than assaying the whole cohort. B case-cohort study samples controls from the entire baseline cohort regardless of subsequent case status, which is the distinguishing difference.

Reference: Gordis Epidemiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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