An investigator wants to study the association between a rare genetic polymorphism and pancreatic cancer. Because enrolling an adequate number of incident cases prospectively would take decades, she identifies a pre-existing cohort of 50,000 adults with stored blood samples, finds all members who later developed pancreatic cancer, and selects a sample of cancer-free members from the same cohort as comparators. Which study design has she used?

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

Explanation

A nested case-control study samples cases and controls from within a defined cohort, with controls selected from those still under observation when each case develops. Exposure data come from baseline measurements taken before disease onset, so temporality is preserved while cost stays low. A retrospective cohort would follow all 50,000 members, which is exactly what the investigator wants to avoid.

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.