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Volume 24, Number 6—June 2018
Research Letter

Symptom-Based Ebola Risk Score for Ebola Virus Disease, Conakry, Guinea

Brecht IngelbeenComments to Author , Anja De Weggheleire, Michel Van Herp, and Johan van Griensven
Author affiliations: Médecins sans Frontières, Conakry, Guinea (B. Ingelbeen, M. Van Herp); Institute of Tropical Medicine, Antwerp, Belgium (A. De Weggheleire, J. van Griensven); European Programme for Intervention Epidemiology Training (EPIET), European Centre for Disease Prevention and Control, Stockholm, Sweden (B. Ingelbeen).

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To the Editor: In their article, Oza et al. proposed a score to risk-stratify Ebola virus disease (EVD) suspected cases while patients in an Ebola treatment center await laboratory confirmation (1). The Ebola symptom-based risk (ESR) score, consisting of 6 symptoms (conjunctivitis, diarrhea, nausea/vomiting, headache, difficulty breathing, loss of appetite), performed well in internal validation, but no external validation was done.

We evaluated the proposed ESR score on 805 EVD-positive and 1,506 EVD-negative case-patients in the Conakry Ebola Treatment Center (ETC), Conakry, Guinea (2). The ESR score yielded an area under the curve of 0.58 (95% CI 0.56–0.61), which is lower than the 0.83 (95% CI 0.79–0.86) Oza et al. reported (Technical Appendix Figure). Using the proposed risk thresholds (i.e., low risk if score <0, medium risk if score = 0, and high risk if score >0), 371 (46%) EVD-positive patients of the Conakry ETC were classified as high risk and 647 (43%) EVD-negative patients as low risk. However, negative and positive predictive values were generally low (Technical Appendix Table). Reasons for poor validation could include differences in applying the general EVD suspect case definition (integration of patients’ contact history); in patient characteristics because organization and access to care for EVD and non-EVD illness was different (patients in holding centers or ETC); in the quality of data collection (symptoms are entirely self-reported); and in underlying diseases of EVD-negative patients.

Our findings underline the importance of external validation in various settings before risk scores are applied outside of the setting within which they were developed, as well as the need to incorporate patient contact history into predictive models. Point-of-care EVD diagnostic platforms can perform reliable confirmatory testing within 90 minutes (3). We argue that, by integrating rapid confirmatory testing in triage, providers can avoid classifying patients by their likelihood of infection with Ebola virus while waiting for laboratory confirmation.

Dr. Ingelbeen, a pharmacist and epidemiologist, worked during the 2014–2016 Ebola outbreak with Médecins sans Frontières in Guinea. He is a European Programme for Intervention Epidemiology Training (EPIET) fellow at Santé publique France. His research interests include emerging and vectorborne infectious diseases.

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Acknowledgment

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References

  1. Oza  S, Sesay  AA, Russell  NJ, Wing  K, Boufkhed  S, Vandi  L, et al. Symptom- and laboratory-based Ebola risk scores to differentiate likely Ebola infections. Emerg Infect Dis. 2017;23:17929. DOIPubMed
  2. Ingelbeen  B, Bah  EI, Decroo  T, Balde  I, Nordenstedt  H, van Griensven  J, et al. Mortality among PCR negative admitted Ebola suspects during the 2014/15 outbreak in Conakry, Guinea: A retrospective cohort study. PLoS One. 2017;12:e0180070 http://dx.plos.org/10.1371/journal.pone.0180070. DOIPubMed
  3. Van den Bergh  R, Chaillet  P, Sow  MS, Amand  M, van Vyve  C, Jonckheere  S, et al. Feasibility of Xpert Ebola Assay in Médecins Sans Frontières Ebola Program, Guinea. Emerg Infect Dis. 2016;22:2106. DOIPubMed

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Cite This Article

DOI: 10.3201/eid2406.171812

Original Publication Date: May 03, 2018

Table of Contents – Volume 24, Number 6—June 2018

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Brecht Ingelbeen, Santé Publique France, Direction des Maladies Infectieuses, 12 rue du Val d'Osne, 94410 Saint-Maurice, France

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Page created: May 17, 2018
Page updated: May 17, 2018
Page reviewed: May 17, 2018
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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