Examkin

Question

Difficulty: MediumStudy Design

A university research consortium is investigating the relationship between early-pregnancy serum levels of a novel inflammatory cytokine and the subsequent risk of developing severe preeclampsia. The investigators have access to an established obstetric biorepository that contains first-trimester blood samples from 50,000 women whose pregnancies were followed to term. Because the multiplex assay for the cytokine is highly expensive, testing all available samples is cost-prohibitive.

To maximize efficiency, the investigators identify all 600 women from the repository who developed severe preeclampsia. For each of these patients, they randomly select two women from the same repository who remained normotensive throughout pregnancy, explicitly matching them by maternal age and exact gestational week at the time of the blood draw. The researchers then thaw and analyze the cytokine levels strictly for these 1,800 selected samples.

Which of the following best describes the epidemiological study design utilized in this investigation?

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

Answer

Nested case-control study
The correct answer is the nested case-control study. In a nested case-control design, cases of a disease that occur in a defined cohort are identified, and for each case, a specified number of matched controls is selected from among those in the cohort who have not developed the disease. The exposure of interest (in this scenario, the inflammatory cytokine) is then measured using biological samples or data that were prospectively collected at baseline, prior to the onset of the disease. This design is highly efficient and cost-effective because it avoids the need to analyze expensive biomarkers for the entire cohort (which would be required in a standard prospective cohort study), while simultaneously eliminating the recall bias and temporal ambiguity associated with traditional retrospective case-control studies.

Step-by-Step Solution

1
Analyze the base population and data collection timeline.
The study utilizes an existing biorepository of 50,000 women who were followed prospectively throughout their pregnancies.
This establishes that the foundational data is from a longitudinal cohort.
2
Determine how the specific analysis groups were selected.
The researchers specifically selected 600 women who developed the disease (cases) and matched them with 1,200 women who did not (controls).
Selecting study groups based on the presence or absence of the outcome characterizes a case-control approach rather than a cohort approach (which groups by exposure).
3
Identify when the exposure was measured.
The exposure (cytokine level) is measured from banked first-trimester serum, collected before the preeclampsia developed.
Applying a case-control analysis to prospectively banked samples within an existing cohort defines a nested case-control design.

Key Concept

Identifying a nested case-control study design
Estimated Time:1m 30s
Rate this question

Topics

Study Design

More questions from this topic