What is the best description of a case-control study?

A case-control study is best described as a comparison between patients who have a specific disease (the cases) and those who do not have the disease (the controls). This design is primarily used to assess the association between an exposure or risk factor and an outcome, typically a disease. Researchers look backward in time to identify how many subjects in each group were exposed to a particular risk factor, allowing them to determine if an association exists between the exposure and the disease.

In this study design, researchers start with the outcome (the presence or absence of disease) and then work backward to analyze the exposures or risk factors that may have contributed to the development of the disease. This approach is particularly useful for studying rare diseases because it is more efficient and less costly than other study designs, such as cohort studies or randomized controlled trials.

The other options describe different types of studies. For example, following patients over time corresponds to a cohort study, which tracks participants to observe outcomes. A descriptive analysis of multiple cases does not fit the case-control framework, as it lacks the comparative aspect. A clinical trial with randomized assignments refers to a randomized controlled trial, which involves assigning subjects to treatment or control groups to test specific interventions.