**Question:** In a population of 100,000, 100 people have pulmonary tuberculosis. Out of 100 people, 10 died. What is the case fatality rate of TB?

**Core Concept:** Case fatality rate (CFR) is a measure of mortality in a specific disease population. It is calculated as the number of deaths divided by the number of cases, multiplied by 100.

**Why the Correct Answer is Right:**

The correct answer is **D** because:

1. The case fatality rate is the number of deaths divided by the number of cases, multiplied by 100.
2. In this scenario, there are 100 cases (100 people with pulmonary tuberculosis) and 10 deaths.
3. So, the calculation for the case fatality rate is: (10 deaths / 100 cases) * 100 = 10%.

**Why Each Wrong Option is Incorrect:**

A) The calculation for option A is incorrect as it only considers deaths but not the number of cases, leading to an overestimation of the CFR.
B) The calculation for option B is incorrect as it only considers cases but not the number of deaths, leading to an underestimation of the CFR.
C) The calculation for option C is incorrect as it includes both deaths and cases in the denominator, making the result meaningless.

**Why Option D is Right:**

Option D correctly calculates the CFR by considering both deaths (10) and cases (100), giving the correct percentage (10%).

**Clinical Pearl:**

Understanding the concept of case fatality rate is crucial in assessing the severity of an illness and comparing the mortality rates of different diseases. In the given scenario, the case fatality rate of pulmonary tuberculosis is 10%. This rate helps healthcare professionals and public health officials make informed decisions about disease surveillance, treatment strategies, and allocate resources accordingly.