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Difficulty: HardMeasures of Association and Impact

Match each clinical research or public health scenario with the most appropriate epidemiological measure of association or impact used to evaluate it.

  • A public health department wants to estimate the total incidence of lung cancer in their region that could theoretically be prevented if asbestos exposure were completely eliminated, taking into account the current prevalence of asbestos exposure in the community.Population Attributable Risk (PAR)
  • An oncology trial evaluates a new targeted therapy versus standard chemotherapy, specifically focusing on the relative rate of progression-free survival at any given instant during a 5-year follow-up, appropriately accounting for patients who drop out or are lost to follow-up.Hazard Ratio (HR)
  • A pharmacy committee requires a concrete metric to understand how many patients must be prescribed a newly approved analgesic instead of a standard NSAID to cause one additional case of severe gastrointestinal bleeding.Number Needed to Harm (NNH)
  • Investigators are conducting a rapid retrospective investigation of a rare, newly identified variant of Guillain-Barré syndrome, comparing the history of a specific prior viral infection between the identified cases and matched healthy individuals.Odds Ratio (OR)
  • A primary care physician explains to a patient that starting a specific supplement decreases their already extremely low baseline risk of a rare metabolic complication by exactly 50%.Relative Risk Reduction (RRR)

Answer

The scenarios correctly match with Population Attributable Risk, Hazard Ratio, Number Needed to Harm, Odds Ratio, and Relative Risk Reduction, respectively.
Each statistical measure is systematically paired with its defining methodological use-case. PAR evaluates community-wide impact based on prevalence; HR evaluates time-to-event data with censoring; NNH translates absolute risk increase into a clinically intuitive patient count; OR estimates association in case-control designs where incidence is unknown; and RRR expresses a proportional reduction without detailing absolute baseline risk.

Step-by-Step Solution

1
Analyze the public health scenario aiming to eliminate a risk factor community-wide.
Identified as requiring Population Attributable Risk (PAR).
PAR specifically estimates the proportion of disease incidence in a total population that can be attributed to a specific exposure, intrinsically accounting for exposure prevalence.
2
Analyze the time-to-event oncology trial with right-censored data.
Identified as requiring a Hazard Ratio (HR).
HR compares instantaneous hazard rates between groups over time and correctly handles right-censoring in survival analysis, unlike basic relative risk.
3
Analyze the requirement for a count of patients needed to experience one additional adverse event.
Identified as Number Needed to Harm (NNH).
NNH is the reciprocal of the Absolute Risk Increase (1/ARI) and provides a concrete integer of patients representing the practical risk of an adverse outcome.
4
Analyze the retrospective study of a rare disease comparing cases to matched healthy controls.
Identified as a case-control study requiring an Odds Ratio (OR).
Case-control studies select patients based on disease status, meaning true population incidence cannot be calculated. Therefore, Relative Risk cannot be mathematically determined, and OR must be utilized.
5
Analyze the scenario describing a proportional decrease in risk independent of the absolute baseline risk.
Identified as Relative Risk Reduction (RRR).
RRR describes the percentage reduction in risk relative to the baseline, which can make treatment effects seem larger than the Absolute Risk Reduction when the underlying baseline risk is very low.

Key Concept

Selection of appropriate measures of association and impact based on study design, data type (e.g., survival data vs. binary outcomes), and clinical or public health goals.
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Topics

Measures of Association and Impact

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