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Difficulty: EasyEpidemiologic Study Designs

A team of pediatric cardiologists identifies all infants born with a specific congenital heart defect at a large regional hospital over the past 5 years. For a comparison group, they randomly select an equal number of infants born without any structural heart defects at the same hospital during the same timeframe. The researchers then interview the mothers of both groups of infants to determine their history of prescription medication use during the first trimester of pregnancy. Which of the following best describes this epidemiologic study design?

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

Answer

The correct answer is a case-control study, as subjects are categorized by disease status and assessed for past exposures.
The study design described is a case-control study. In this observational design, subjects are initially selected based on the presence of a disease or outcome (infants with the congenital heart defect) or the absence of the disease (healthy infants). Once the cases and controls are established, the investigators look backward in time to determine the frequency of a particular exposure (maternal medication use) in both groups to calculate an odds ratio.

Step-by-Step Solution

1
Identify how the researchers selected the participant groups.
The groups were selected based on whether the infants had a congenital heart defect or did not have a congenital heart defect.
The defining feature of a study design is often how the subjects are initially grouped.
2
Determine the temporal direction of the investigation.
After grouping by the outcome, the researchers looked backward in time (via interviews) to assess a past exposure (medication use during pregnancy).
Looking backward from an outcome to find an exposure is characteristic of specific observational studies.
3
Combine the grouping method and temporal direction to name the design.
Selecting by outcome and looking back for exposure defines a case-control study.
This matches the classic definition of a case-control design.

Key Concept

In a case-control study, patients with a specific disease (cases) and people without the disease (controls) are selected, and then their history of past exposure is compared.
Estimated Time:45s
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Epidemiologic Study Designs

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