What are the different classifications of dengue?

Classifications of Dengue

Dengue is classified into three main categories according to the 2009 WHO revised classification: Dengue without Warning Signs, Dengue with Warning Signs, and Severe Dengue, which provides better clinical utility for identifying cases requiring heightened care compared to the traditional 1997 classification. 1, 2, 3

Traditional WHO Classification (1997)

The traditional classification system categorized dengue into:

1. Dengue Fever (DF):

   • Acute febrile illness with headache, retro-ocular pain, muscle/joint pain, and rash
   • Laboratory confirmation through virus isolation, antibody testing, or antigen detection

2. Dengue Hemorrhagic Fever (DHF):

   • Acute febrile illness with minor or major bleeding phenomena
   • Thrombocytopenia (≤100,000/mm³)
   • Evidence of plasma leakage (hemoconcentration with hematocrit increased by ≥20% or other evidence of increased capillary permeability)

3. Dengue Shock Syndrome (DSS):

   • Meets all criteria for DHF
   • Additionally presents with hypotension or narrow pulse pressure (≤20 mm Hg) 4

Revised WHO Classification (2009)

The revised classification system, which has demonstrated higher sensitivity (92.1% vs. 39.0%) and specificity (78.5% vs. 75.5%) for identifying severe cases requiring intensive care, categorizes dengue into:

1. Dengue without Warning Signs:

   • Fever with two of the following: nausea/vomiting, rash, aches/pains, leukopenia
   • Represents approximately 31% of dengue cases 5

2. Dengue with Warning Signs:

   • Dengue with any of the following warning signs:
     • Abdominal pain or tenderness
     • Persistent vomiting
     • Clinical fluid accumulation
     • Mucosal bleeding
     • Lethargy/restlessness
     • Liver enlargement
     • Increasing hematocrit with decreasing platelets
   • Represents approximately 58.4% of dengue cases 5
   • Requires strict observation and medical intervention

3. Severe Dengue:

   • Characterized by:
     • Severe plasma leakage leading to shock or fluid accumulation with respiratory distress
     • Severe bleeding
     • Severe organ involvement (liver, CNS, heart, or other organs)
   • Represents approximately 10.6% of dengue cases 5
   • Requires emergency treatment and intensive care 1, 3

Clinical Significance of Classifications

• The revised classification better captures the clinical spectrum and severity of dengue, with higher sensitivity for identifying cases requiring intensive care (92.1% compared to 39.0% for the traditional classification) 2

• Laboratory parameters correlate with disease severity:

  • Leukopenia (<4,000 cells/mm³) is present in 64.68% of dengue patients and shows significant association with disease severity
  • Thrombocytopenia (<150,000 cells/mm³) is present in 40.48% of patients and strongly correlates with severity 6

• Warning signs are critical indicators for progression to severe disease:

  • Vomiting and abdominal pain are the two most common warning signs
  • At least one warning sign is present in 83-100% of DHF cases 7

Practical Application

• The revised classification is more effective in identifying severe cases requiring intensive management, though it may create approximately twice the workload for healthcare personnel compared to the traditional system 7

• Monitoring for warning signs is essential for early identification of progression to the critical phase, which typically occurs around defervescence 6

• Plasma leakage detection techniques vary in sensitivity:

  • Hemoconcentration detects 44.7% of cases
  • Chest X-ray increases detection to 86.3%
  • Ultrasonography is most sensitive, detecting up to 100% of plasma leakage cases 7

• The revised classification better standardizes clinical management, raises awareness about unnecessary interventions, and matches patient categories with specific treatment instructions 3