Relative survival compares the survival of a group to the survival expected in the group if they did not have the disease.

• A. The survival of a diseased group compared to expected survival of a population without the disease, matched by age and sex.
• B. The observed survival in the general population without consideration of disease status.
• C. The incidence rate of the disease in the cohort.
• D. The proportion alive at the end of the study.

Answer: (A)

Relative survival compares how the survival of people with a disease stacks up against how long similar people in the general population would be expected to live if they did not have the disease. It uses life tables to estimate the expected survival for individuals matched on factors like age and sex (and sometimes calendar year or region), and then compares the actual observed survival in the diseased group to that expectation. This yields a ratio that reflects excess mortality attributable to the disease, without needing cause-of-death data.

The best description is the one that states the survival of a diseased group compared to the expected survival of a population without the disease, matched by age and sex. The other options describe related but different ideas: observed survival in the general population without considering disease status omits the disease group; the incidence rate concerns new cases, not survival; and the proportion alive at the end of the study is simply a crude survival proportion, not a comparison to a matched non-diseased expectation.