A group of public health researchers is investigating an outbreak of a rare gastrointestinal illness. They enroll 50 patients who recently developed the illness and 100 healthy individuals from the same community. The researchers then review the participants' dietary histories over the past month to determine if they consumed a specific brand of locally produced cheese.
Among the 50 ill patients, 30 had consumed the cheese. Among the 100 healthy individuals, 20 had consumed the cheese.
Based on the study design and the provided data, which of the following is the most appropriate measure of association and its correctly calculated value?
- AOdds ratio of 1.5
- BRelative risk of 3.0
- CRelative risk of 6.0
- Odds ratio of 6.0Answer
- EAttributable risk of 40%
Answer
Odds ratio of 6.0
The study groups participants based on their disease status (ill patients versus healthy individuals) and then looks back in time to assess their exposure to the cheese. This is the defining characteristic of a case-control study. In a case-control study, researchers cannot directly measure incidence, so the relative risk cannot be calculated. Instead, the odds ratio is the appropriate measure of association. The odds ratio is calculated as (Odds of exposure in cases) / (Odds of exposure in controls) = (30/20) / (20/80) = (1.5) / (0.25) = 6.0.
Step-by-Step Solution
Key Concept
Identifying a case-control study design and calculating the corresponding Odds Ratio.