Within an ongoing prospective cohort of 50,000 adults with stored baseline blood samples, researchers identify all subjects who develop pancreatic cancer over 15 years and select a sample of cancer-free subjects from the same cohort, matched on age and sex. They then compare baseline biomarker levels between the two groups. This design is called:

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

Explanation

In a nested case-control study, cases and controls are both drawn from inside a defined cohort, and exposure data come from measurements made before disease onset. This retains the temporal security of the cohort while costing far less than assaying the whole cohort. B case-cohort differs because controls form a random subcohort sampled at baseline rather than being individually matched to each case.

Reference: Rothman, Greenland and Lash, Modern Epidemiology, 3rd ed.

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Written and medically reviewed by the StethoPrep medical team.