Abstract
The study investigated combining Department of Defense (DoD) and Veterans Administration (VA) outpatient datasets for disease cluster detection. Results of retrospective scan statistics over 4 years were compared using both separate and joined data. Combining data sources increased the background alert rate by a manageable 1-10% across run sets. Clustering evidence of known outbreaks found in separate DoD and VA runs persisted when data sets were combined. Some clusters found only when the data were combined persisted over several days and may have indicated small events not reported in either system.