**Core Concept**
Screening programs are designed to detect diseases at an early stage, often before symptoms appear, with the goal of reducing morbidity and mortality. The effectiveness of a screening program can be measured by its ability to identify previously unrecognized disease.

**Why the Correct Answer is Right**
The amount of previously unrecognized disease diagnosed by a screening effort is known as the "yield" or "prevalence" of the disease in the screened population. This can be calculated as the number of new cases detected through screening divided by the total number of individuals screened. Effective screening programs aim to maximize this yield by targeting high-risk populations and using sensitive diagnostic tests.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incomplete and does not provide a valid answer.
* **Option B:** This option is unclear and does not describe a recognized measure of screening effectiveness.
* **Option C:** This option may refer to the "incidence" of disease, which is the number of new cases occurring within a population over a specific period, rather than the amount of previously unrecognized disease diagnosed through screening.

**Clinical Pearl / High-Yield Fact**
A well-designed screening program should have a high sensitivity (ability to detect true positives) and a low false-positive rate to maximize the yield of previously unrecognized disease.

**Correct Answer: B. Disease prevalence.**