Which statement correctly characterizes a nested case-control study?
- A Exposure and outcome are both measured simultaneously at a single point in time
- B It is a randomized design in which participants are allocated to exposure status before outcome occurrence
- C Cases and controls are sampled from within a previously defined prospective cohort, preserving temporal sequence of exposure measurement ✓
- D Each case serves as its own control across different exposure periods
Correct answer: C. Cases and controls are sampled from within a previously defined prospective cohort, preserving temporal sequence of exposure measurement
Explanation
In a nested case-control study, all incident cases emerging from an ongoing cohort are compared with a sampled subset of cohort members free of the outcome, often matched on follow-up time. Because exposure data were collected prospectively before disease onset, the design avoids recall bias and permits expensive assays such as stored biomarkers on a fraction of the cohort. Option D describes a case-crossover design, and option A describes a cross-sectional survey.
Reference: Park's Textbook of Preventive and Social Medicine, 26th ed.
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