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Difficulty: MediumStudy Design

An occupational medicine research group is investigating the health outcomes of workers who were exposed to a specific, newly synthesized industrial solvent during a 6-month manufacturing period 15 years ago. Only 350 workers were ever exposed to this chemical before the manufacturing process was permanently altered. The researchers aim to determine if these exposed workers have an increased incidence of various hepatic and neurologic disorders compared to unexposed workers at the same facility. Comprehensive medical records and employment logs from the past two decades are available for all workers. Which of the following epidemiological study designs is most appropriate for this investigation?

  1. Retrospective cohort studyAnswer
  2. B
    Case-control study
  3. C
    Prospective cohort study
  4. D
    Cross-sectional study
  5. E
    Case-crossover study

Answer

Retrospective cohort study
The correct study design is one that identifies an exposed group in the past using existing records, identifies an unexposed group from the same time period, and traces both groups forward using historical data to the present to assess the incidence of multiple outcomes. This perfectly describes a retrospective cohort study, which is the absolute optimal design for evaluating a rare, historical exposure with a long latency period when comprehensive records are available.

Step-by-Step Solution

1
Analyze the exposure characteristics.
The exposure (novel industrial solvent) is rare, having affected only 350 workers.
Rare exposures are most efficiently studied using cohort designs, which group subjects based on exposure status rather than disease status.
2
Analyze the outcome characteristics and study goals.
The researchers want to study multiple long-term outcomes (hepatic and neurologic disorders) and measure their incidence.
Cohort studies are uniquely suited to evaluate multiple outcomes resulting from a single exposure and can calculate true disease incidence.
3
Evaluate the temporal relationship and available data.
The exposure occurred 15 years ago, and comprehensive medical records are available spanning from that time up to the present.
Because the exposure is historical and data already exists across the 15-year latency period, a retrospective cohort study avoids the wait and expense of a prospective design.

Key Concept

Selection of a retrospective cohort study design for rare historical exposures
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Topics

Study Design

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