Which statement best describes a case definition?

• A. A uniform set of criteria used to classify whether a person has the disease for surveillance
• B. A list of all suspected cases
• C. A diagnostic test result
• D. A manual for laboratory procedures

Answer: (A)

In public health surveillance, a case definition provides a uniform set of criteria used to classify whether a person has the disease for surveillance. This standard ensures that cases are identified consistently across clinicians and over time, allowing accurate measurement of disease burden and trends. A case definition may combine clinical features, laboratory evidence, and sometimes epidemiologic information, and it often includes categories like suspected, probable, or confirmed based on the strength of evidence.

The other ideas aren’t about the standardized criteria used for classification: listing all suspected cases is about case finding rather than applying a uniform definition; a single diagnostic test result isn’t enough to classify a case since tests can vary in accuracy and require clinical context; and a manual for laboratory procedures describes how tests are performed, not how to classify cases for surveillance.