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Difficulty: MediumStudy Design

A city health commission is analyzing a recent localized cluster of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in a specific neighborhood. The researchers identify 80 residents who tested positive for the virus and developed symptoms during a two-week period. They also recruit 160 residents from the same neighborhood who tested negative and remained asymptomatic during the same timeframe. Both groups are administered a detailed questionnaire regarding their attendance at various local indoor venues (e.g., gyms, restaurants, grocery stores) over the preceding month. The researchers aim to determine which specific venues are associated with the highest risk of viral transmission by comparing the frequency of attendance between the two groups. Which of the following best describes the study design utilized in this investigation?

  1. A
    Retrospective cohort study
  2. B
    Cross-sectional study
  3. Case-control studyAnswer
  4. D
    Nested case-control study
  5. E
    Case-crossover study

Answer

Case-control study
The correct answer is a case-control study because the researchers first identified individuals based on their outcome status (those with SARS-CoV-2 infection versus those without) and then looked retrospectively at their exposure histories (attendance at indoor venues). This design is highly efficient for investigating outbreaks and analyzing multiple potential risk factors for a specific disease.

Step-by-Step Solution

1
Identify how the study groups were formed.
The researchers formed one group of patients who tested positive for the virus (cases) and another group who tested negative (controls).
Understanding the basis for group selection (exposure vs. outcome) is the primary step in determining the study design.
2
Determine the direction of temporal inquiry.
After forming the groups based on disease status, the researchers asked participants about their venue attendance over the preceding month.
Establishing the timeline of data collection relative to the outcome distinguishes retrospective designs from prospective ones.
3
Synthesize the findings to classify the study.
Selecting subjects based on the presence or absence of a disease and looking backward in time for prior exposures defines a case-control design.
This matches the classic methodological framework for investigating outbreaks.

Key Concept

Identifying a case-control study design by recognizing that subjects are selected based on outcome status before assessing historical exposures.
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Study Design

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