Abstract
Rapid early detection and control of Ebola virus disease (EVD) is contingent on accurate case definitions. Using an epidemic surveillance dataset from Guinea, we analyzed an EVD case definition developed by the World Health Organization (WHO) and used in Guinea. We used the surveillance dataset (March–October 2014; n = 2,847 persons) to identify patients who satisfied or did not satisfy case definition criteria. Laboratory confirmation determined cases from noncases, and we calculated sensitivity, specificity and predictive values. The sensitivity of the defintion was 68.9%, and the specificity of the definition was 49.6%. The presence of epidemiologic risk factors (i.e., recent contact with a known or suspected EVD case-patient) had the highest sensitivity (74.7%), and unexplained deaths had the highest specificity (92.8%). Results for case definition analyses were statistically significant (p<0.05 by χ2 test). Multiple components of the EVD case definition used in Guinea contributed to improved overall sensitivity and specificity.
Highlights
Rapid early detection and control of Ebola virus disease (EVD) is contingent on accurate case definitions
Population Dataset As part of national surveillance for EVD in West Africa, a standard case investigation form was completed for all patients who were suspected of having EVD [16], and diagnostic laboratory testing was conducted for patient specimens
The sensitivity was 14.2%, the specificity was 92.8%, the positive predictive value (PPV) was 72.0%, and the negative predictive values (NPV) was 45.2% (p
Summary
Rapid early detection and control of Ebola virus disease (EVD) is contingent on accurate case definitions. 1 approach is a highly sensitive (i.e., broad) clinical case definition that enables all possible signs and symptoms of EVD to be detected, with confirmation relying on highly specific diagnostic testing This approach can be valuable in a setting in which diagnostic testing and healthcare facilities are available to test and safely care for all persons who satisfy the case definition. Another approach is the use of a more stringent clinical case definition for EVD for patients who do not have known risk factors (i.e., contact with EVD cases) and enables a lower threshold for suspecting EVD if a person has had risk for exposure This strategy could be essential in resource-limited areas where testing facilities are not readily available or where there might be delays in laboratory results. Rapid detection of EVD and institution of appropriate infection control procedures in these areas rely heavily on quick patient identification and presumptive diagnosis before laboratory confirmation
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