Which study has a case-control design?
A. Participants are assessed at baseline and then again every 3 months for two years for occurrence of disease
B. Patients who recovered from COVID-19 infection are matched and compared with patients who recovered from the seasonal flu for harmful lasting effects
C. A random sample of auto mechanics is tested for lead poisoning
D. Patients are randomly selected to use one of 2 drugs for arthritis symptoms and followed over time to assess treatment response
The correct answer and explanation is:
The correct answer is B. Patients who recovered from COVID-19 infection are matched and compared with patients who recovered from the seasonal flu for harmful lasting effects.
Explanation:
A case-control study is an observational study design used to identify factors that may contribute to a particular outcome, typically a disease or condition. It compares individuals who have the outcome or disease of interest (cases) with individuals who do not have the outcome (controls). Researchers look backward in time to assess exposure or characteristics that might explain the difference in outcomes between the two groups.
In option B, patients who recovered from COVID-19 (cases) are compared with patients who recovered from seasonal flu (controls). The goal is to assess harmful lasting effects, which is the outcome of interest. Since the two groups are matched and compared based on their past illness and current effects, this reflects the retrospective and comparative nature of case-control studies.
The other options do not fit a case-control design:
- Option A describes a cohort study where participants are followed over time to see who develops the disease. This is prospective and longitudinal.
- Option C describes a cross-sectional study where a random sample of auto mechanics is tested at a single point in time for lead poisoning. This assesses exposure and outcome simultaneously.
- Option D describes a randomized controlled trial where participants are randomly assigned to one of two treatment groups and followed prospectively for response. This is an experimental design.
In summary, the case-control study is characterized by identifying cases and controls based on outcome status and looking back to compare exposures or characteristics. Option B clearly matches this pattern, making it the correct choice.