Recorded presentation

Amanda D. Castel, MD MPH¹, David Blythe, MD, MPH², Alvina K. Chu, MHS², and Marsha G. Davenport, MD MPH². (1) EIS Officer, Centers for Disease Control and Prevention/Epidemiology and Disease Control Program, Maryland Department of Health and Mental Hygiene, 201 West Preston Street, Baltimore, MD 21201, 410-767-6031, acastel@dhmh.state.md.us, (2) Epidemiology and Disease Control Program, Maryland Department of Health and Mental Hygiene, 201 West Preston Street, Baltimore, MD 21201

Objectives: Syndromic surveillance systems, such as the National Capitol Region Emergency Department Syndromic Surveillance System (NCREDSSS), have recently been implemented to detect outbreaks, particularly those potentially caused by bioterrorism. NCREDSSS uses chief complaints from emergency department (ED) logs to assign illnesses to one of eight syndrome categories. The proportions of each syndrome are analyzed to detect aberrancies that might identify possible bioterrorism-related outbreaks. Operational since 2001, NCREDSSS has not detected gastroenteritis outbreaks reported by more traditional mechanisms. In this study, syndrome definitions were modified to attempt to detect previously reported outbreaks.

Methods: The existing gastrointestinal syndrome definition was redefined to include only chief complaints of vomiting, diarrhea or gastroenteritis. ED logs were recoded retrospectively to determine if this narrower syndrome definition would have detected a reported large Maryland gastroenteritis outbreak.

Results: During the 20 days reviewed, there were 2,544 gastrointestinal cases before recoding (average:127.2 cases/day). Under the new definition, there were 1,038 cases (average: 51.9 cases/day), and an average of 41.8% (range 27.3-56.5%) fewer cases/day in the gastrointestinal syndrome category were identified. Two gastrointestinal aberrancies were generated; however neither clearly corresponded to the actual reported outbreak.

Conclusions: Manipulating case definitions to be more specific did not aid in the detection of a large gastroenteritis outbreak. The current system of reporting outbreaks continues to be more reliable than NCREDSSS. These findings emphasize the need for evaluation of standard syndromic case definitions, particularly for syndrome categories with many cases (such as gastrointestinal syndrome), in order to improve the effectiveness of syndromic surveillance systems.

Learning Objectives:

• 1.Understand how reported outbreaks can be used to validate syndromic surveillance systems.
• 2.Discuss issues related to defining syndromic surveillance case definitions.
• 3.List several limitations associated with the use of syndromic surveillance systems.
• 4.Identify methods for the standard evaluation of syndromic surveillance systems.

Keywords: Bioterrorism, Surveillance

Presenting author's disclosure statement:
I do not have any significant financial interest/arrangement or affiliation with any organization/institution whose products or services are being discussed in this session.

Recorded presentation