Types of a surveillance system

About attributes

• Attributes are characteristics or properties of a system
• The definitions vary a lot
• This book follows ECDC Handbook Data quality monitoring and surveillance system evaluation
• Closely related is data quality (which is completeness and validity)

The underestimation pyramid

Underestimation pyramid Norovirus

Underestimation pyramid

Underestimation pyramid Ebola

Underestimation pyramid

Definitions around underestimation

Attributes around underestimation

Sensitivity

• Definition: Proportion of cases in a population that are reported. Underascertainment and underreporting
• How to measure: Compare to gold standard, capture-recapture

Internal completeness

• Definition: the number of completed data fields out of the total number of data fields
• How to measure: Analyse the data

External completeness

• Definition: whether the data reflect the true number of reported cases - ‘sensitivity of reporting’ This corresponds to underreporting
• How to measure: Capture-recapture

Validity

Representaion of validity. Do you really see the truth behind all our mirros and lenses? Image done by bing image creator

Internal validity

• Definition: extent of errors within the system - ‘errors in reporting’
• How to measure: Analyse the reporting system

External validity

• Definition: whether the information recorded about the cases is correct
• How to measure: Test against a gold standard

Timeliness

Vocabulary of different time measurements

Timeliness

• Definition: speed between steps in a public health surveillance system
• How to measure: Analyse database

Usefulness

Representaion of usefulness. What can you do with the information? Image done by bing image creator

• Defintion: contribution to the prevention and control of infectious diseases
• How to measure: Survey

Representativeness

• Defintion: accuracy of describing the occurrence of a health-related event across time, place, person
• How to measure: Population covered by surveillance divided by the total number

Simplicity

• Definition: refers to both its structure and ease of operation.
• How to measure: Survey

Flexibility

• Definition: the amount of adaptibility to changing information needs
• How to measure: Survey

Acceptability

• Definition: Acceptability is the willingness of persons and organisations to participate
• How to measure: Survey