A researcher has complete follow-up records for a cohort of 10,000 factory employees. Whenever a worker develops occupational asthma, comparison subjects are selected from among workers who were under observation at that same point in time and had not yet developed the disease. This design is best described as:

• A Case-cohort study
• B Concurrent prospective cohort study
• C Historical prospective cohort study
• D Nested case-control study ✓

Explanation

Sampling controls from the risk set, meaning those still under observation and disease-free at the moment each case occurs, is incidence density sampling, the hallmark of a nested case-control study conducted within a defined cohort. The distractor, case-cohort design, differs because its control series is sampled once from the entire cohort at baseline regardless of whether controls later become cases, and it does not use time-matched risk sets.

Reference: Gordis Epidemiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.