A researcher has a cohort of 50,000 adults with banked baseline blood samples. Ten years later she identifies all 300 incident cases of lymphoma and selects 900 cancer-free members of the same cohort as controls, then assays a stored biomarker in these 1,200 subjects only. Which design is this?
- A Nested case-control study ✓
- B Classic case-control study
- C Case-cohort study
- D Historical prospective study
Correct answer: A. Nested case-control study
Explanation
In a nested case-control study, cases and controls are drawn from within a defined cohort, and controls must be persons who were still under follow-up and free of the disease at the time the case was diagnosed. It retains the temporal advantages of a cohort while allowing expensive assays on only a sample. In a case-cohort study the comparison group is a subcohort sampled at baseline irrespective of subsequent case status.
Reference: Gordis Epidemiology, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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