**Question:** Active method to detect undiagnosed cases in apparently healthy people is -

A. Screening
B. Active surveillance
C. Health promotion and disease prevention
D. Health education

**Core Concept:**
The question is testing the understanding of a diagnostic strategy used to identify individuals with undiagnosed conditions in a population of seemingly healthy people. In this context, active methods involve proactive measures to detect diseases or abnormalities in a group of people without a prior referral or indication of illness.

**Why the Correct Answer is Right:**
The correct answer, **A. Screening**, refers to a deliberate attempt to identify individuals with a particular condition or risk factor by systematic examination or testing in a defined population, regardless of symptoms or contact history. This is crucial in early disease detection, allowing timely intervention and improved prognosis.

In this context, screening is different from passive surveillance, which relies on individuals seeking medical attention for symptoms or concerns. Active surveillance involves actively searching for individuals at risk or with subtle symptoms, while health promotion and disease prevention focus on modifying risk factors or preventing diseases, and health education aims to improve health literacy, not necessarily disease detection.

**Why Each Wrong Option is Incorrect:**

**Option B. Active surveillance:** Although active surveillance is essential in certain settings (e.g., cancer surveillance), it is not the general solution for undiagnosed cases in apparently healthy people.

**Option C. Health promotion and disease prevention:** This focuses on reducing risk factors and preventing diseases, not specifically detecting undiagnosed cases in healthy individuals.

**Option D. Health education:** Health education aims to improve health literacy and knowledge, not specifically for disease detection in healthy individuals.

**Clinical Pearl:**

Active screening plays a significant role in early disease detection, allowing timely intervention and improved prognosis. In healthcare, it is essential to differentiate between screening and other preventive strategies like health promotion, disease prevention, and health education. Understanding these distinctions helps in employing appropriate measures to enhance public health outcomes.