Which statement best describes how a case-control study starts?

Which statement best describes how a case-control study starts?

• A. Starts with disease status and looks backward to exposures
• B. Starts with exposure and follows to disease
• C. Randomizes exposure
• D. Observes population cross-section

Answer: (A)

Starting with disease status and looking backward to exposures is how a case-control study operates. In this design, you begin with individuals who have the disease (cases) and those without it (controls), then compare their past exposures to see which group was more likely to have been exposed. This retrospective approach makes case-control studies efficient for studying rare diseases and allows estimation of the odds of exposure among cases versus controls, usually expressed as an odds ratio. To place it in context, starting with exposure and following forward to disease describes a cohort study, where you watch people over time to see who develops the outcome. Randomizing exposure is characteristic of a randomized controlled trial, not an observational study. A cross-sectional study looks at exposure and disease status at a single point in time without following individuals forward. Thus, the hallmark way a case-control study starts is by selecting based on disease status and then looking back to determine prior exposures.

Starting with disease status and looking backward to exposures is how a case-control study operates. In this design, you begin with individuals who have the disease (cases) and those without it (controls), then compare their past exposures to see which group was more likely to have been exposed. This retrospective approach makes case-control studies efficient for studying rare diseases and allows estimation of the odds of exposure among cases versus controls, usually expressed as an odds ratio.

To place it in context, starting with exposure and following forward to disease describes a cohort study, where you watch people over time to see who develops the outcome. Randomizing exposure is characteristic of a randomized controlled trial, not an observational study. A cross-sectional study looks at exposure and disease status at a single point in time without following individuals forward. Thus, the hallmark way a case-control study starts is by selecting based on disease status and then looking back to determine prior exposures.