title: Criteria of "persistent vomiting" in the WHO 2009 warning signs for dengue case classification.
abstract: BACKGROUND
  Dengue is a viral disease that spreads rapidly in the tropic and subtropic regions of the world and causes 22,000 deaths annually. In 2009, the World Health Organization (WHO) released a new classification of dengue infections, which divided them into three categories: dengue without warning sign (D), dengue with warning sign (DWS), and severe dengue (SD). However, researchers have been using different criteria to define persistent vomiting; therefore, we aimed to evaluate the ability of the number of vomiting times in early prediction of SD development among D/DWS patients.
  
  
  METHODS
  A hospital-based cohort study was conducted in Ben Tre-south of Vietnam. We enrolled confirmed dengue patients with D and DWS at admission. The final classification was determined on the discharged day for every patient based on the classification of WHO 2009 without using vomiting symptom, using the receiver operating characteristic (ROC) curve to evaluate the ability of the number of vomiting times in early prediction of SD development among D/DWS patients.
  
  
  RESULTS
  The prevalence of vomiting symptom was higher in SD group than D/DWS group (92 versus 46 %, p = 0.006), and the median of the number of vomiting times was higher in SD group than D/DWS group (2.5 versus 0, p = 0.001). To distinguish SD from D/DWS, the ROC curve of the number of vomiting episodes showed that the area under the curve was 0.77; with the cut point of two, the sensitivity and specificity were 92 and 52 %, respectively.
  
  
  CONCLUSIONS
  The number of vomiting times could be a good clinical sign which can early predict SD from the group of D/DWS. We suggest the definition of persistent vomiting should be vomiting two times or more per day.
authors.affiliation: University of Medicine and Pharmacy, 217 Hong Bang, District 5, Ho Chi Minh City, 70000 Vietnam.
authors.forename: Nguyen Lam
authors.initials: NL
authors.lastname: Vuong
authors.affiliation: Department of Immunogenetics, Institute of Tropical Medicine (NEKKEN), Leading Graduate School Program, and Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Dao Huy
authors.initials: DH
authors.lastname: Manh
authors.affiliation: Department of Immunology and Microbiology, Pasteur Institute Ho Chi Minh City, Ho Chi Minh City, Vietnam.
authors.forename: Nguyen Thi
authors.initials: NT
authors.lastname: Mai
authors.affiliation: Nguyen Dinh Chieu Hospital, Ben Tre, Ben Tre Province Vietnam.
authors.forename: Le Hong
authors.initials: le H
authors.lastname: Phuc
authors.affiliation: Children's Hospital No.1, Ho Chi Minh City, Vietnam.
authors.forename: Van Thuy
authors.initials: VT
authors.lastname: Luong
authors.affiliation: University of Medicine and Pharmacy, 217 Hong Bang, District 5, Ho Chi Minh City, 70000 Vietnam.
authors.forename: Vo Duy
authors.initials: VD
authors.lastname: Quan
authors.affiliation: Department of Immunology and Microbiology, Pasteur Institute Ho Chi Minh City, Ho Chi Minh City, Vietnam.
authors.forename: Nguyen Van
authors.initials: NV
authors.lastname: Thuong
authors.affiliation: Department of Immunology and Microbiology, Pasteur Institute Ho Chi Minh City, Ho Chi Minh City, Vietnam.
authors.forename: Nguyen Thi Phuong
authors.initials: NT
authors.lastname: Lan
authors.affiliation: Nguyen Dinh Chieu Hospital, Ben Tre, Ben Tre Province Vietnam.
authors.forename: Cao Thi My
authors.initials: CT
authors.lastname: Nhon
authors.affiliation: Department of Clinical Product Development, Institute of Tropical Medicine (NEKKEN), Leading Graduate School Program, and Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Shusaku
authors.initials: S
authors.lastname: Mizukami
authors.affiliation: Nguyen Dinh Chieu Hospital, Ben Tre, Ben Tre Province Vietnam.
authors.forename: Nguyen Ngoc
authors.initials: NN
authors.lastname: Doan
authors.affiliation: Department of Immunology and Microbiology, Pasteur Institute Ho Chi Minh City, Ho Chi Minh City, Vietnam.
authors.forename: Vu Thi Que
authors.initials: VT
authors.lastname: Huong
authors.affiliation: Department of Clinical Product Development, Institute of Tropical Medicine (NEKKEN), Leading Graduate School Program, and Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Nguyen Tien
authors.initials: NT
authors.lastname: Huy
authors.affiliation: Department of Immunogenetics, Institute of Tropical Medicine (NEKKEN), Leading Graduate School Program, and Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hirayama
keywords: Dengue; Prediction; Severity; Vomiting; Warning sign