How do case-fatality rate and proportionate mortality differ?

• A. Case-fatality rate relates to those with the disease; proportionate mortality is the share of deaths due to a specific cause
• B. Case-fatality rate is the only mortality rate
• C. They are the same thing
• D. Proportionate mortality is a rate of disease incidence

Answer: (A)

The main idea here is that these two measures use different denominators and describe different things about mortality. Case-fatality rate looks at people who actually have the disease and asks: among those cases, what fraction die from the disease? It’s like a conditional risk: deaths due to the disease divided by the number of diagnosed cases. For example, if 100 people are diagnosed and 5 die, the case-fatality rate is 5%.

Proportionate mortality, on the other hand, asks: among all deaths in a population during a given period, what fraction are caused by this specific disease? It uses total deaths as the denominator, so it reflects the disease’s share of all deaths, not the risk to those who have the disease. If 1,000 people die in a year and 50 die from the disease, the proportionate mortality is 5%.

So the best description is that the case-fatality rate relates to those with the disease, while proportionate mortality is the share of deaths due to a specific cause. The two are different because they focus on different populations (disease cases vs. all deaths) and answer different questions (fatality among cases vs. contribution to overall mortality).