Examkin

Soru

Zorluk: OrtaStudy Design

An epidemiology research group is utilizing data and stored biological specimens from a large, ongoing prospective cohort study of 80,00080,000 healthy adults that began 1515 years ago. The researchers want to investigate whether elevated baseline serum levels of a newly identified inflammatory cytokine, Cytokine-X, are associated with an increased risk of developing multiple sclerosis (MS). During the 1515-year follow-up period, 120120 participants developed MS. Measuring Cytokine-X is technically demanding and highly expensive; therefore, it is financially impossible to assay the stored baseline serum samples of all 80,00080,000 participants. The investigators plan to measure the cytokine levels in the baseline serum of the 120120 participants who developed MS and compare them to the baseline serum of a randomly selected subgroup of participants who remained free of the disease, matched for age and sex. Which of the following best describes this study design?

  1. Nested case-control studyCevap
  2. B
    Retrospective cohort study
  3. C
    Case-crossover study
  4. D
    Propensity score-matched cohort study
  5. E
    Cross-sectional study

Cevap

Nested case-control study
The scenario describes a nested case-control study. In this design, cases of a disease that occur in a defined cohort are identified, and a subset of participants who have not developed the disease are selected as controls. The primary advantage is cost and resource efficiency; it allows investigators to analyze expensive biomarkers (like Cytokine-X) using prospectively collected baseline data without needing to process samples for the entire cohort of 80,00080,000 people. Because the samples were collected at baseline prior to disease onset, recall bias is eliminated and a clear temporal sequence is preserved.

Adım Adım Çözüm

1
Identify the parent population.
The researchers are using participants from an ongoing prospective cohort of 80,00080,000 adults.
Recognizing that the study originates from a well-defined cohort narrows down the methodological possibilities.
2
Determine how the comparison groups are formed.
Participants are selected based on whether they developed the outcome (the 120120 MS cases) or did not (randomly selected controls).
Grouping by outcome status (disease vs. no disease) indicates a case-control approach rather than a cohort approach.
3
Analyze the timing of exposure measurement.
The exposure (Cytokine-X) is measured from biological specimens collected at baseline, years before the disease developed.
This establishes clear temporality, which combined with the outcome-based sampling within a cohort, confirms the nested case-control design.

Anahtar Kavram

A nested case-control study involves identifying cases and a sample of controls from within a predefined prospective cohort to efficiently study expensive or difficult-to-measure baseline exposures.
Bu soruyu puanla

Konular

Study Design

Bu konudan daha fazla soru