Dengue classification: current WHO vs. the newly suggested classification for better clinical application?

INTRODUCTION: There has been confusion regarding the clinical classification of dengue. The current WHO classification used since the 70s classifies dengue into dengue fever (DF), dengue hemorrhagic fever (DHF), dengue shock syndrome (DSS). In 2009, a new classification of dengue proposed by WHO Tropical Disease Research (TDR) was published in the WHO TDR 2009 dengue guidelines. This new classification classifies dengue into dengue (D), dengue with warning signs (DW) and severe dengue (SD).
OBJECTIVE: To compare the effectiveness in clinical management between the current WHO classification and the newly suggested classification (TDR) and to assess the 4 criteria of the DHF case definition of the current WHO classification for possible modification. MATERIAL AND
METHOD: A prospective study of suspected dengue patients admitted to the Dengue Unit, Queen Sirikit National Institute of Child Health between June-August 2009 was done. All cases were managed according to the Thai National Dengue Guidelines 2008. The final diagnoses were based on the current WHO Classification together with dengue laboratory confirmation. TDR classification was applied later by the author, using the data from the present study case report forms of each patient. Statistical analysis comparing clinical and laboratory data between each group of patients was done by using SPSS version 14.
RESULTS: Total 274 confirmed dengue patients and 24 non-dengue febrile illnesses (ND) were used for analysis. There were 180 DF (65.7%), 53 DHF grade I (19.3%), 19 DHF grade II (6.9%), 19 DHF grade II (6.9%) and 3 DHF grade IV (1.1%) as classified by the current WHO classification while the suggested TDR classified 85 (31%), 160 (58.4%) and 29 (1.1%) as D, DW and SD respectively. At least one of the warning signs were found in 50, 53.3, 83, 88.2, 100 and 100% of ND, DF, DHF grade I, DHF grade II, DHF grade III and DHF grade IV patients. Vomiting and abdominal pain were the 2 most common warning signs found in both ND and dengue patients. Intensive monitoring and careful medical and i.v. fluid management were needed for 94 DHF patients compared to 189 DW and SD patients by the new TDR classification. There were 8 DSS patients who had AST > 1,000U and one patient presented with encephalopathy. These 8 patients cannot be classified properly in the current WHO classification. One non-dengue patient who presented with gastrointestinal bleeding was classified as SD. Bleeding and/or positive tourniquet test was found in and 69.7% of DHF patients. Plasma leakage detected using hemoconcentration, chest x-ray (CXR) and ultrasonography. Hemoconcentration could detect plasma leakage in 44.7% and CXR added up evidence of plasma leakage to 86.3%. Ultrasonography was the most sensitive technique to add evidence of plasma leakage up to 100%. Platelet < or = 100,000 cells/mm3 was found in 93.5% of DHF patients.
CONCLUSION: Current WHO classification is recommended for continuing use because the newly suggested TDR classification creates about 2 times the workload to health care personnel. In addition, the TDR classification needs dengue confirmatory tests. More than 90% of DHF defined by WHO case definition are dengue confirmed. However, current WHO classification needs to be modified for more simple and friendly use. The suggested modification is to address plasma leakage as the major criteria. Tourniquet test positive or bleeding symptoms can be considered as minor criteria. Unusual dengue is proposed to be added to the current WHO classification to cover those patients who do not fit with the current WHO classification.