Health and Demographic Surveillance Systems (HDSSs) provide a useful framework for tracking demographic and health dynamics in defined geographical areas over time. HDSS captures information on residence, updates vital events and covers the whole or part of a district where all individuals, their relationships, ages as well as other attributes, are recorded longitudinally along with events affecting population dynamics including birth, death and migrations (in and out). Most importantly, HDSS sites monitor cause of death as a major indicator of population health. Together with data on residence and demographic events the HDSS captures several other types of socio-economic data including household wealth and education status as additional important information for population health profiles. At the same time the HDSS co-exists with a facility-based data source in a form of Health Management Information System (HMIS) which captures health services attendance, diagnosis, service and treatment data as individuals come into contact with the formal health system for either preventive or curative services from one of the health facilities serving the Demographic Surveillance Area (DSA).

Integrating the two data sources would provide both the numerator and the denominator population for computation of both disease incidence rates in the population and health service coverage rates in the health system, essential data health system analysis, health planning and policy formulation which is currently lacking. These linkages would as well improve management and health service provision and policies in rural settings where data collection on vital information is weak. For instance, linking the two databases will enhance active follow up of treatment cohorts and tracing patients on specific treatment regimes to their location if need be (e.g. people on ACTs, IPTp; IPTi; TB DOTS, Ante and post-natal care) in order to understand system performance.

The Data linkage task team aims to provide a means to link information generated from the two data systems in the INDEPTH Effectiveness Studies Platform is essential to the success of the Platform. It will develop, adapt and implement a practical mechanism to appropriately link the HDSS with facility-based data from HMIS in a way that is appropriate to individual HDSS and Health System settings for the respective countries. This would be achieved by providing a unique identification tag for the records of individuals when they visit the facility. In order to make sure the privacy of both HDSS members and patients is safeguarded the system will ensure that the health providers cannot become aware of information the DSS holds about the individual while at the same time HDSS staff and analysts cannot access individual patient and medical records of the health system. The data linkage will be designed to allow analysis of anonymised data while still retaining population attributes from the DSS database.