Surveillance Key Points Dr. Oswaldo S. Medina Gómez

DEFINITION  Continuous and systematic process of collection, analysis, interpretation, and dissemination of descriptive information for monitoring and investigate health problems

OBJECTIVES  Descriptive epidemiology of health problems.  Links to services.  Links to research.  Evaluation of interventions.  Projections and planners.  Education and policy.

SURVEILLANCE SYSTEM  Case definition.  Population under surveillance.  Cycle of surveillance.  Confidentiality.  Incentives to participation.

APPROACHES TO SURVEILLANCE  Active or passive surveillance?  Notifiable disease reporting.  Laboratory- based surveillance.  Volunteer providers.

APPROACHES TO SURVEILLANCE  Registries.  Surveys.  Information system  Sentinel events.  Record linkages.

REGISTRIES  Are listings of all occurrences of a disease, or category of disease within a defined area.  Registries collect relatively detailed information and may identify patients for long-term follow-up for specific laboratory or epidemiologic investigation.

SURVEY  Provide a method for monitoring behaviors associated with disease, personal attributes that affect disease risk, knowledge/attitudes that influence health behaviors, use of health services, and self-reported disease occurrence.

INFORMATION SYSTEM  Are data bases collected for general, rather that disease-specific purposes, which can applied to the surveillance of specific conditions.

SENTINEL EVENTS  The occurrence of rare disease known to be associated with a specific exposure can alert health officials to situations where others may have been exposed to a potential hazard.

SENTINEL EVENTS  Surveillance for sentinel events can be used to identify situations where public health investigation or intervention is required.

RECORD LINKAGES  Linkage of surveillance records to an independent data source can be used to identify previously undetected cases and thus measure and improve the completeness of surveillance

ANALYSIS OF SURVEILLANCE DATA  The analysis of surveillance is descriptive and straightforward, using standard epidemiologic techniques.  Comparisons between groups may require steps to assess and control for confounding, and more advanced analytic techniques may be required.

ATTRIBUTIONS OF SURVEILLANCE  Sensitivity.  Timeliness.  Representativeness.  Predictive value.

ATTRIBUTIONS OF SURVEILLANCE  Accuracy and completeness of descriptive information.  Simplicity.  Flexibility.  Acceptability.

SENSITIVITY  Extent does the system identify all the events in the target population.  For purposes of monitoring trends, low sensitivity may be acceptable if sensitivity is consistent over time and detected events are representative.

TIMELINESS  Entire cycle of information flow, ranging from collection to dissemination.

REPRESENTATIVENESS  Events detected through the surveillance system represent persons with the condition of interest in the target population

ACCURACY AND COMPLETENESS OF DESCRIPTIVE INFORMATION  Forms of reporting health events often include descriptive personal information