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Table 1 The CDC standard performance indicators to assess the usefulness of surveillance system [12]

From: Assessment of electronic disease early warning system for improved disease surveillance and outbreak response in Yemen

Indicator Definition
Data quality depends on the completeness and validity of eDEWS data, and the accuracy of its reports.
Timeliness refers to the speed or interval between steps in the eDEWS. The time interval between any two sequential steps can be assessed.
Simplicity refers to the simple structure and ease in applying the procedure to improve the timeliness of the eDEWS.
Positive predictive value (PPV) reflects the proportion of confirmed cases or alerts from the condition under surveillance. eDEWS allows for the calculation of a PPV at the level of case detection depending on the number of alerts generated and the proportion of confirmed alerts as truly under surveillance.
Sensitivity The sensitivity of a surveillance system can be considered on two levels. At the level of case reporting, sensitivity refers to the proportion of cases of a disease detected by the surveillance system. Sensitivity also can refer to the system’s overall ability to detect outbreaks, including the ability to monitor changes in the number of cases in a population over time.
Acceptability indicates the willingness of health workers and partners to participate in the surveillance system.
Flexibility means the ease with which a) information or conditions can be changed as needed, b) eDEWS can accommodate a new disease, c) changes can be made in case definitions, and d) variations can be made in reporting sources.
Representativeness defines disease occurrence over time and the characteristics of a covered population.