A 32-year-old female from Mumbai presents to the emergency department on day 5 of illness with fever, severe headache, retro-orbital pain, and myalgia. Her husband had similar symptoms 3 days ago. On examination, she has a petechial rash on the trunk and a positive tourniquet test. Her platelet count is 85,000/µL, and NS1 antigen is positive. She is haemodynamically stable with no signs of plasma leakage. What is the most likely classification of her dengue illness?

Explanation

## Classification of Dengue Illness **Key Point:** The 2009 WHO classification divides dengue into three categories: dengue without warning signs, dengue with warning signs, and severe dengue. ### Case Analysis This patient presents with: - Classic dengue symptoms (fever, headache, retro-orbital pain, myalgia) - **Positive tourniquet test** — a recognized warning sign per 2009 WHO criteria - **Petechial rash** — haemorrhagic manifestation - Thrombocytopenia (85,000/µL — platelet count <100,000/µL is a warning sign) - Haemodynamic stability (no shock) - No evidence of plasma leakage (no ascites, pleural effusion, or ≥20% rise in haematocrit) ### 2009 WHO Dengue Warning Signs (any ONE qualifies) 1. Abdominal pain or tenderness 2. Persistent vomiting 3. Clinical fluid accumulation (ascites, pleural effusion) 4. Mucosal bleeding 5. Lethargy / restlessness 6. Liver enlargement >2 cm 7. **Rapid decline in platelet count with concurrent rise in haematocrit** 8. **Positive tourniquet test / any bleeding tendency** Per WHO 2009 (*Dengue: Guidelines for Diagnosis, Treatment, Prevention and Control*), a **positive tourniquet test** is explicitly listed as a warning sign. Additionally, a platelet count falling to ≤100,000/µL in the context of dengue illness is a laboratory warning sign. This patient therefore meets criteria for **dengue with warning signs**. ### Dengue Classification Table | Feature | Dengue (No WS) | Dengue with WS | Severe Dengue | |---------|---|---|---| | Fever + systemic symptoms | Yes | Yes | Yes | | Warning signs present | No | **Yes** | Yes | | Plasma leakage | No | No | Yes (≥20% Hct rise) | | Haemodynamic status | Stable | Stable | Unstable / shock | | Organ impairment | No | No | Yes | **High-Yield:** A positive tourniquet test is NOT merely a haemorrhagic manifestation — it is explicitly a **warning sign** in the 2009 WHO classification. The absence of plasma leakage rules out severe dengue, but the positive tourniquet test and thrombocytopenia (<100,000/µL) place this patient firmly in the **dengue with warning signs** category. **Clinical Pearl:** Dengue shock syndrome (DSS) and dengue haemorrhagic fever (DHF) are older WHO 1997 terminologies. The 2009 revision replaced them with "severe dengue." This patient is haemodynamically stable with no plasma leakage, so neither severe dengue nor DSS applies. **Reference:** WHO (2009). *Dengue: Guidelines for Diagnosis, Treatment, Prevention and Control*. Geneva: WHO Press. Chapter 2, pp. 25–27.