Understanding Dengue Test: Importance, Types, and Procedures

Test selection depends on timing of illness: (1) DAY 1-5 of fever (early illness) — NS1 ANTIGEN test is BEST; detects dengue viral protein in blood before antibodies form; sensitivity 70-90% days 1-3, drops after day 5; sample = single blood draw; (2) DAY 5+ of fever — IgM antibody test becomes positive; detects immune response; specific for recent infection; (3) IgG antibody — high in secondary dengue (previous dengue + new infection) — indicates increased severity risk; useful in outbreak epidemiology; (4) RT-PCR (viral RNA) — most accurate early (day 1-5) but expensive; typically reserved for confirmed severe cases, atypical presentations, research; not routine; (5) NS1 + IgM combination panel — covers both early and later phases; commonly ordered when timing unclear. ADDITIONAL essential tests during dengue: (1) CBC with platelet count — repeat every 12-24 hours; watch for drop below 100,000 (warning), below 20,000 (bleeding risk); (2) Hematocrit — rising Hct indicates plasma leakage (severe dengue warning); (3) LFT — elevated in most dengue; hepatitis component; (4) Coagulation profile if bleeding suspected. Modern dengue management is guided by daily monitoring, not just diagnostic test at admission.

Dengue phases and warning signs: FEBRILE PHASE (Days 1-3): sudden high fever 39-40°C, severe body ache, headache, retro-orbital pain, joint pain (‘breakbone fever’), nausea, vomiting, rash. Most patients recover from here. CRITICAL PHASE (Days 3-6): as fever DECREASES (defervescence), 5-10% develop severe complications — PLASMA LEAKAGE. Warning signs of severe dengue: (1) Persistent vomiting (>3 episodes in hour); (2) Severe abdominal pain (constant, not just cramping); (3) Bleeding — nose, gums, bruising, blood in vomit/stool/urine, menstrual excess; (4) Restlessness or lethargy; (5) Cold clammy extremities; (6) Rapid weak pulse, drop in BP; (7) Difficulty breathing; (8) Marked drop in platelet count (<50,000); (9) Rising hematocrit >20%; (10) Reduced urine output. RECOVERY PHASE (Days 6-10): fluid reabsorbs, rash may recur, gradual improvement. When to seek emergency care immediately: any of the warning signs above; especially if fever suddenly drops but patient appears WORSE (not better) — critical phase warning; sudden severe abdominal pain; bleeding from any site; altered mental state; dizziness on standing. India-specific: dengue outbreaks worst in monsoon (July-October); Bangalore, Delhi, Kolkata, Chennai, Ahmedabad among high-burden cities; mosquito breeding in stored water containers (bucket, cooler, flower pot, tyre); Aedes mosquito bites during daytime especially early morning + late afternoon; use repellent (DEET 20-30% or picaridin), full-sleeve clothing, mosquito nets.

Dengue treatment is supportive — NO specific antiviral: (1) FLUIDS are the cornerstone — oral in mild cases (WHO ORS, coconut water, dal ka pani, buttermilk, fresh fruit juice), IV in severe cases (crystalloids like Ringer’s lactate); careful fluid balance critical — under-hydration + shock danger, over-hydration + pulmonary oedema danger; (2) PARACETAMOL for fever (500-1000mg every 4-6 hours, max 4g/day); AVOID aspirin, ibuprofen, other NSAIDs (increase bleeding risk); AVOID intramuscular injections (haematoma risk); (3) MONITORING — daily CBC (platelet + hematocrit), symptom assessment, fluid intake/output balance, vital signs; frequency depends on severity; (4) HOSPITALISATION indicated for: any warning sign, high-risk patients (pregnancy, elderly, comorbidities), inability to maintain oral hydration, platelet count <50,000. PLATELET TRANSFUSION — commonly over-used; guidelines: (1) Platelet transfusion NOT indicated for count alone (up to 20,000-30,000 without bleeding — no transfusion needed); (2) Indicated for: active bleeding + thrombocytopenia; platelet count <10,000 with high-risk factors; before invasive procedures; (3) Random donor platelets are less expensive but need multiple units to raise count meaningfully; single donor platelets (SDP) are more expensive; (4) Papaya leaf extract — no strong evidence but widely used; likely safe; do NOT replace medical care. FLUID MANAGEMENT: crystalloids first-line; colloids if inadequate response; blood transfusion if bleeding-related anaemia. RECOVERY: most uncomplicated cases recover 7-10 days; fatigue can persist weeks. Post-dengue: rare complications include prolonged fatigue, joint pain, hair loss; secondary dengue increases severity risk — dengue vaccination (Dengvaxia, QDenga) only for previously infected individuals in specific contexts.