**Question:** All are true about Case control study EXCEPT:

A. It is a retrospective study.
B. It is designed to find the cause of an event.
C. It is a prospective study.
D. It is the most appropriate study design to evaluate the efficacy of a drug.

**Correct Answer:** A. It is a retrospective study.

**Core Concept:** A case-control study is a type of observational study that examines the association between a specific exposure or event (case) and the likelihood of developing a particular disease or condition (control). It involves retrospectively identifying cases and controls from records or databases and collecting data on their exposures or events. The study design helps in determining the risk factors associated with a disease or condition.

**Why the Correct Answer is Right:** The correct answer is not a retrospective study because case-control studies are not typically conducted in a retrospective manner. Instead, they are designed to collect data on past exposures or events for both cases and controls. The study is conducted after the disease or condition has already occurred.

**Why Each Wrong Option is Incorrect:**

A. It is a retrospective study: As mentioned above, case-control studies are not conducted retrospectively but prospectively to identify cases and controls.

B. It is designed to find the cause of an event: Case-control studies aim to identify risk factors associated with a specific disease or condition, not to determine the cause of an event.

C. It is a prospective study: Case-control studies are conducted after the disease or condition has occurred, making it a retrospective study, not a prospective one.

D. It is the most appropriate study design to evaluate the efficacy of a drug: Case-control studies are primarily used to investigate the association between exposures and diseases or conditions, not to evaluate drug efficacy.

**Clinical Pearl:** While case-control studies are valuable in identifying risk factors and establishing causality, they may not be the most suitable design for evaluating the efficacy or effectiveness of a treatment or intervention. In such cases, randomized controlled trials (RCTs) are typically used to determine the effectiveness of a treatment or intervention. Understanding the strengths and limitations of different study designs is essential for selecting the most appropriate research design for a particular research question.