2014.ISDS.Abstracts.Final.pdf


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ISDS 2014 Conference Abstracts

A Syndrome Definition Validation Approach for Ebola 
Virus Disease
Dino Rumoro1, Shital Shah1, Marilyn Hallock1, Gillian Gibbs*1, Gordon Trenholme1 and 
Michael J. Waddell2

1Emergency Medicine, Rush University Medical Center, Chicago, IL, USA; 2Pangaea Information Technologies, Chicago, IL, USA

Objective
To develop and validate an Ebola virus disease syndrome 

definition within the GUARDIAN (Geographic Utilization of 
Artificial Intelligence in Real-Time for Disease Identification and 
Alert Notification) surveillance system.

Introduction
The 2014 Ebola outbreak in West Africa is one of the largest Ebola 

outbreaks in history. Early detection is critical for rapid initiation 
of treatment, infection control and emergency response plans. 
To facilitate clinicians’ ability to detect Ebola, various syndrome 
definitions have been developed.

Methods
To create and validate a detailed syndrome definition for Ebola, we 

utilized the literature based methodology developed and documented 
by GUARDIAN researchers.1,2 The syndrome definition utilized 
clinical signs and symptoms that were documented in historical Ebola 
cases.

A testing sample of 800 randomly selected emergency department 
cases (i.e., true negative cases) and 200 synthetically generated cases 
(i.e., true positive cases) was created. These 1,000 sample cases were 
evaluated by the GUARDIAN surveillance system to determine the 
probability of matching the Ebola syndrome definition. A probability 
of 90% was utilized to designate positive Ebola cases.

We identified the main signs and symptoms contributing to the 
identification of Ebola cases and conducted statistical performance 
metrics. Clinical review of the false positive and false negative cases 
along with a sample of true positive and true negative cases was 
conducted by a board certified emergency physician and an infectious 
diseases expert.

Results
The Ebola syndrome definition was developed with 14 articles (10 

used for developing the syndrome definition, and 4 used for testing the 
definition). The sample size for these articles was between 1 and 217 
positive Ebola cases, with a total of 678 cases across the 14 articles. 
The publication timeframe for the articles was from 1977 to 2005. 
Some of the main signs and symptoms from the historical cases that 
contribute to the Ebola syndrome definition are presented in Table 1.

The initial results for the sample testing data showed accuracy, 
sensitivity, and specificity were 96%, 89%, and 97%, respectively. 
There were a total of 22 false negative and 27 false positive cases.

Conclusions
The initial Ebola syndrome definition utilized by the GUARDIAN 

surveillance system contains similar signs and symptoms to the current 
CDC case definition, but also includes additional signs and symptoms 
such as abdominal tenderness, thrombocytopenia, nausea, malaise, 
weakness, and loss of appetite. In addition, the GUARDIAN system 
provides the relative importance of identified signs and symptoms and 
allows for proactive surveillance of emergency department patients 
in real-time. Though we didn’t include epidemiologic risk factors, 

such as travel to an infected region or contact with an infected person 
in the syndrome definition, GUARDIAN has above 89% sensitivity 
and specificity. Thus, inclusion of epidemiologic risk factors would 
further enhance the early detection of Ebola and possibly other 
viral hemorrhagic fevers when used with the appropriate high risk 
population.

Table 1. Main signs and symptoms of the Ebola syndrome definition.

* Signs and symptoms that are included in the Centers for Disease Control and 
Prevention (CDC) Ebola case definition.

Keywords
Ebola; GUARDIAN; syndrome definition

Acknowledgments

GUARDIAN is funded by the US Department of Defense, Telemedicine 
and Advanced Technology Research Center, Award numbers 
W81XWH-09-1-0662 and W81XWH-11-1-0711.

References

1. Silva J, Rumoro D, Hallock M, Shah S, Gibbs G, Waddell M, Thomas K. 
Disease profile development methodology for syndromic surveillance 
of biological threat agents. Emerging Health Threats Journal. 2011; 
4(11129).

2. Silva J, Shah S, Rumoro D, Hallock M, Gibbs G, Waddell M. A Novel 
Syndrome Definition Validation Approach for Rarely Occurring 
Diseases. Online Journal of Public Health Informatics. 2013; 5(1).

*Gillian Gibbs
E-mail: Gillian_Gibbs@rush.edu    

Online Journal of Public Health Informatics * ISSN 1947-2579 * http://ojphi.org * 7(1):e156, 2015