Comparison of dengue case classification schemes and evaluation of biological changes in different dengue clinical patterns in a longitudinal follow-up of hospitalized children in Cambodia

Background The World Health Organization (WHO) proposed guidelines on dengue clinical classification in 1997 and more recently in 2009 for the clinical management of patients. The WHO 1997 classification defines three categories of dengue infection according to severity: dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS). Alternative WHO 2009 guidelines provide a cross-sectional classification aiming to discriminate dengue fever from dengue with warning signs (DWWS) and severe dengue (SD). The primary objective of this study was to perform a comparison of two dengue classifications. The secondary objective was to describe the changes of hematological and biochemical parameters occurring in patients presenting with different degrees of severity during the course of the disease, since progression to more severe clinical forms is unpredictable. Methodology/Principal findings We performed a prospective, monocentric, cross-sectional study of hospitalized children in Cambodia, aged from 2 to 15 years old with severe and non-severe dengue. We enrolled 243 patients with acute dengue-like illness: 71.2% were dengue infections confirmed using quantitative reverse transcription PCR or NS1 antigen capture ELISA, of which 87.2% and 9.0% of DF cases were respectively classified DWWS and SD, and 35.9% of DHF were designated SD using an adapted WHO 2009 classification for SD case definition. Systematic use of ultrasound at patient admission was crucial for detecting plasma leakage. No difference was observed in the concentration of secreted NS1 protein between different dengue severity groups. Lipid profiles were different between DWWS and SD at admission, characterized by a decrease in total cholesterol, HDL cholesterol, and LDL cholesterol, in SD. Conclusions/Significance Our results show discrepancies between the two classifications, including misclassification of severe dengue cases as mild cases by the WHO 1997 classification. Using an adapted WHO 2009 classification, SD more precisely defines the group of patients requiring careful clinical care at a given time during hospitalization.


An increase in hematocrit greater than or equal to 20% above average for given age, sex and population
We used the hematocrit normal range of 32-40% for children aged from 2 to 6 years old ([2-6] y/o) and 32-49% for those aged over 6 and up to 15

A drop in the hematocrit following volume-replacement treatment equal to or greater than 20% of baseline.
For all children with hematocrit levels greater than the mean values defined above for both age categories at Visit 1 or Visit 2, we looked for a 20% drop of hematocrit levels between Visit 2 and Visit 1, Visit 3 and Visit 2, and Visit 3 and Visit 1.

Signs of plasma leakage such as pleural effusion, ascites, or hypoproteinemia.
The presence of pleural effusion, ascites, and hepatomegaly was evaluated by ultrasonographic examination performed during the three scheduled visits. However, the proteinemia level was not measured in this study.
Dengue shock syndrome (DSS) is defined as the presence of all four DHF criteria, plus evidence of circulatory failure. In this study we used weak pulse and narrow pulse pressure (defined by a difference in systolic and diastolic blood pressure of at most 20 mmHg) or hypotension with respect to age (age < 5 years: ≤ 80 mmHg; age ≥ 5 years: ≤ 90 mmHg). Additional signs such as cold and clammy skin, and restlessness, were also considered. All of these were calculated or registered at Visits 1 and 2. Finally, note that subtle differences between DHF1/DHF2 and between DDS3/DSS4 were not taken into consideration.

B. WHO 2009 classification
Due to the difficulties in prospectively applying DHF case definition criteria for the WHO 1997 classification scheme as described earlier, a new classification scheme known as WHO 2009 was defined, separating dengue cases into severe dengue and non-severe dengue. Non-severe dengue patients are divided into two subgroups: patients with warning signs (DWWS) and those without (D-nonWS).

Dengue without warning signs (D-nonWS)
is defined by fever plus at least two of the following signs: nausea, vomiting, rash, aches and pains.

Dengue with warning signs (DWWS)
is defined as an association of clinical signs with laboratory findings; detection therefore requires strict observation and good medical care. Warning signs include abdominal pain or tenderness, vomiting, petechiae, purpura, bleeding nose or gum, hematemesis, and conjunctival hemorrhage, and were investigated at all visits. Clinical fluid accumulation (pleural effusion and ascites fluid) and liver enlargement were evaluated using ultrasonographic examination as previously described for DHF. We adapted WHO 2009 classification by using ultrasound that gave us the opportunity to semi-quantify the degree of fluid accumulation, providing a more accurate clinical diagnosis in discriminating between DWWS and severe dengue (SD): (i) minimal amount of liquid was considered as mild plasma leakage i.e. a warning sign (DWWS); (ii) moderate or abundant amount of liquid was considered as severe dengue, possibly leading to aggravation with respiratory distress (SD). We also considered an increase in the hematocrit above the normal range as previously defined (i.e., 36% for [2-6] y/o and 40.5% for ]6-15] y/o children) concurrent with thrombocytopenia (≤ 100x10 9 /L) as a significant marker of DWWS at Visits 1 and 2. However, all patients received an intravenous fluid infusion at the time of hospital admission, which could have contributed to normalizing or decreasing their hematocrit levels. Thus, we also considered a rapid decrease in platelet count (drop ≥ 50% between consecutive visits) as another significant marker of DWWS. Finally, an isolated thrombocytopenia (i.e., at only one visit) was not considered as a warning sign.
Severe dengue (SD) was defined by (i) severe plasma leakage leading to shock (DSS) or fluid accumulation with respiratory distress, (ii) severe bleeding as evaluated by the clinician, or (iii) severe organ involvement comprising hepatic injury (AST or ALT levels ≥ 1000 IU/L). Moreover, moderate or abundant pleural effusion detected by ultrasound was also considered a clinical sign which may lead to respiratory distress. Such patients were also classified as SD.