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ISDS 2012 Conference Abstracts

Coverage and Timeliness of Combined Military and
Veteran Surveillance Systems
Howard S. Burkom1, Yevgeniy Elbert1, Carla Winston2, Julie Pavlin*3, Cynthia Lucero-
Obusan2 and Mark Holodniy2

1Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA; 2Veterans Health Administration, Palo Alto, CA, USA;
3Armed Forces Health Surveillance Center, Silver Spring, MD, USA

Objective
We determined the utility and effective methodology for combin-

ing patient record information from the Departments of Veterans Af-
fairs (VA) and Defense (DoD) health surveillance systems.

Introduction
An objective of the Joint VA/DoD BioSurveillance System for

Emerging Biological Threats project is to improve situational aware-
ness of the health of combined VA and DoD populations. DoD and
VA both use versions of the Electronic Surveillance System for the
Early Notification of Community-Based Epidemics (ESSENCE).
With a retrospective outpatient data collection available, we analyzed
relative coverage and timeliness of the two systems to understand po-
tential benefits of a joint system.

Methods
We used the US Office of Management and Budget’s core-based

statistical area (CBSA) to group data from the respective systems by
megapolitan (>1 million), metropolitan (50,000-1 million) and mi-
cropolitan (10,000-50,000) areas. We performed frequency analyses
and mapped coverage of the VA and DoD medical systems in these
CBSAs. To determine comparability, we compared International
Classification of Diseases, 9th Revision (ICD-9) code usage from
2007-2010 by age group in the respective systems and then formu-
lated a working definition of influenza-like illness (ILI). We then
compared CBSA-level temporal detection timeliness in the two sys-
tems for the H3N2 epidemic of 2007-9 and the H1N1 pandemic in
2009.

Results
We identified a total of 939 CBSAs, with generally diffuse geo-

graphic coverage by VA facilities and higher concentration in larger
metro and mega areas for DoD facilities. Of the 51 mega CBSAs, all
have at least one VA facility and 63% have a DoD facility. Coverage
is sparser for the metro CBSAs and lighter still for the micro CBSAs
(Table 1). Although the VA coverage is greater, in many CBSAs with
dual coverage, the DoD visit volume is comparable or greater. Pa-
tient age distribution differs sharply, with >85% of the VA patients
over 45 years of age compared to 22% of DoD patients. For all
CBSAs, the overall VA/DoD visit ratio is 1.92, but the ratios for 0-17
years is 0.004, 18-44 years 0.33, 45-64 years 5.20 and >65 years
11.63. 

Based on an analysis of ICD-9 codes used in the two systems, the
DoD uses symptom-based ILI codes far more frequently than the VA,

especially codes for diseases often seen in children (e.g., otitis
media). Analysis of ILI-related codes assigned in both systems led to
a common code set for comparative analysis. From applying alerting
algorithms to visit counts based on this code set, detection was bet-
ter in DoD data for 57% and 77% of CBSAs for seasonal and pan-
demic influenza, respectively, and better in VA data for 37% and 14%
of CBSAs (Table 2). The VA system performed better during the typ-
ical H3N2 seasonal flu compared to the H1N1 outbreak. The DoD
system performed better during the H1N1 pandemic, although out-
performed the VA for both.

Conclusions
The coverage analysis demonstrates two complementary surveil-

lance systems with evident benefits to a fused national health picture.
The VA system patient volume roughly doubles the DoD system, and
provides better geographic coverage in smaller CBSAs; however, the
DoD includes younger populations, better coverage in strategic metro
areas, and more pre-diagnostic ILI coding. From analysis of both out-
breaks, relative timeliness could be improved in 92% of CBSAs with
access to both systems, with more information provided in CBSAs
where only one type of facility exists.

Table 1. Counts of CBSAs containing VA and DoD facilities

Table 2. Relative timeliness by CBSAs with both DoD and VA facilities with
a minimum average of 2 ILI visits/week

Keywords
Syndromic surveillance; Merged systems; Government

*Julie Pavlin
E-mail: julie.pavlin@us.army.mil

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 5(1):e39, 2013