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Difficulty: MediumMeasures of Disease Frequency and Association

Match each epidemiological study design or clinical scenario to the most appropriate measure of disease frequency or association used to report its findings.

  • Investigators identify patients with systemic lupus erythematosus and a comparable group without the disease, then retrospectively ascertain their history of Epstein-Barr virus infection.Odds ratio
  • A study follows a large group of healthy nurses for 20 years to compare the rate of new breast cancer diagnoses in those who work night shifts versus those who work day shifts.Relative risk
  • In a randomized trial for a new lipid-lowering agent, researchers calculate a metric to communicate how many patients must receive the intervention to prevent one major cardiovascular event.Number needed to treat
  • Public health officials conduct a state-wide screening initiative to determine the proportion of the population that currently has a body mass index greater than 30 kg/m230\text{ kg}/\text{m}^2.Prevalence

Answer

Case-control studies match to Odds ratio; cohort studies match to Relative risk; calculating clinical impact of an intervention matches to Number needed to treat; and point-in-time population surveys match to Prevalence.
Each study design fundamentally restricts which epidemiological measures can be validly calculated. Case-control studies must use odds ratios because incidence is unknown. Cohort studies allow for relative risk calculation because new cases are tracked over time. Clinical trials often report 'number needed to treat' (1 / absolute risk reduction) to show practical efficacy for patients. Cross-sectional studies measure a snapshot in time, yielding point prevalence.

Step-by-Step Solution

1
Identify the underlying study design or objective described in each scenario.
The scenarios describe a case-control study (lupus vs. healthy), a cohort study (nurses followed over time), an intervention efficacy calculation, and a cross-sectional survey.
The study design dictates which mathematical epidemiological measures are valid and appropriate to calculate.
2
Match the case-control scenario to its primary metric.
Case-control studies map to the Odds ratio.
Because the researcher fixes the number of diseased patients (cases), true incidence cannot be calculated. Thus, the odds of exposure are compared instead of the risk of disease.
3
Match the cohort scenario to its primary metric.
Cohort studies map to Relative risk.
Cohort studies follow groups over time based on exposure, allowing for the direct calculation of incidence rates (risk), which are then compared using a relative risk (risk ratio).
4
Match the clinical trial impact and survey scenarios.
Preventing one event maps to Number needed to treat, while a point-in-time cross-sectional snapshot maps to Prevalence.
These map directly to their foundational epidemiological definitions.

Key Concept

Appropriate Application of Epidemiological Measures by Study Design
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Topics

Measures of Disease Frequency and Association

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