Cost-effectiveness of a GIS-based targeted Chlamydia trachomatis intervention policy

Background – Many Illinois counties sustain a chlamydia incidence rate significantly higher than the state average. Current intervention policy is based upon state-provided testing coupled with locally-developed community interventions. Many local health departments (L-HD) lack the training and resources to implement innovative interventions.

Objective – The objective was to determine if a policy of state health department (S-HD) assistance in the development of a Geographic Information System (GIS)-based targeted intervention at the local level would be cost-effective.

Methods – County chlamydia cases for 2005 were geocoded using a GIS and stratified at the census block group (CBG) level by case count and concentration. Census Bureau data at the county and CBG level were collected, and maps and demographic data charts were developed and provided to each LHD. Participants had ten weeks to implement an intervention to targeted areas.

Results – GIS analysis revealed that chlamydia does not cluster as tightly as other STDs, though CBG stratification revealed areas of high incidence or concentration that were previously unknown. LHD staff completed their interventions during the study period, though all reported having few resources available. Preliminary results suggest an insignificant impact upon local incidence.

Conclusions – All participants found the state-provided data useful in developing a targeted intervention. Lack of significant impact may be due to the lack of funding, the short experimental period, and the relative mildness of infection. Furthermore, due to chlamydia's more spatially distributed nature, the use of GIS and targeted interventions for this disease may not be cost-effective.