In surveillance, a case definition is used to standardize which of the following?

• A. The Criteria for Including Cases in a Registry
• B. The Risk Factors for the Disease
• C. The Etiologic Agents of Infections
• D. The Rate of Hospital Acquisitions

Answer: (A)

Case definitions in surveillance standardize who is counted as a case by specifying the exact criteria used to classify an individual as having the disease or condition. By agreeing on clinical signs, laboratory confirmation, the time frame of onset, and sometimes the setting, data from different sites become comparable and can be pooled into a registry or surveillance system. This consistency prevents variability in what gets counted as a case from distorting trends and analyses.

Risk factors describe attributes that may increase the likelihood of disease but do not determine who is counted as a case. Etiologic agents focus on the cause of infections, not on who qualifies as a reportable case. The rate of hospital acquisitions is an outcome measure derived from surveillance data, not the mechanism used to standardize inclusion in the registry.