Which statement best describes a hallmark of retrospective cohort studies?

Which statement best describes a hallmark of retrospective cohort studies?

• A. Prospective data collection
• B. Randomization
• C. Use of existing records to determine exposure status at baseline
• D. Random assignment

Answer: (C)

In a retrospective cohort study, exposure status is determined from existing records at the baseline, and outcomes are assessed using those historical data. This use of preexisting data to classify who was exposed at the start is what defines the design. Prospective data collection would involve gathering data going forward from the present, while randomization or random assignment are features of experimental designs, not typical of retrospective observational studies.

In a retrospective cohort study, exposure status is determined from existing records at the baseline, and outcomes are assessed using those historical data. This use of preexisting data to classify who was exposed at the start is what defines the design. Prospective data collection would involve gathering data going forward from the present, while randomization or random assignment are features of experimental designs, not typical of retrospective observational studies.