How do you assess the severity of dengue fever in a patient?

Dengue Severity Assessment

Assess dengue severity by classifying patients into three categories based on warning signs, hemodynamic status, and laboratory parameters: dengue without warning signs (outpatient management), dengue with warning signs (hospitalization for monitoring), or severe dengue (immediate intensive care). 1

Classification Framework

The WHO classification system stratifies patients into distinct severity categories that directly guide management decisions:

Dengue Without Warning Signs

• Patients present with fever plus at least one of the following: nausea, vomiting, rash, headache, retro-orbital pain, myalgia, arthralgia, positive tourniquet test, or leukopenia 1
• These patients can be managed as outpatients if they have platelet count >100,000/mm³ without rapid decline, stable hematocrit without hemoconcentration, no comorbidities, and reliable daily follow-up available 1
• Fever with retro-orbital pain and severe myalgia/arthralgia are characteristic features 2

Dengue With Warning Signs (Critical Phase Indicators)

Monitor daily for these warning signs that predict progression to severe disease:

• Persistent vomiting that prevents adequate oral hydration is a key warning sign requiring hospitalization 3, 1
• Abdominal pain or tenderness significantly predicts severe disease (OR 1.92; 95% CI 1.35-2.74) 4
• Clinical fluid accumulation (pleural effusion in 20.7% or ascites in 15.3% of patients) strongly predicts severe disease (OR 4.61; 95% CI 2.29-9.26) 5, 4
• Mucosal bleeding including epistaxis, gum bleeding, or GI bleeding increases risk of severe dengue (OR 1.57; 95% CI 1.13-2.19) 6, 4
• Lethargy or restlessness indicates potential progression 3, 6
• Rising hematocrit with falling platelet count (>20% increase in hematocrit from baseline) signals plasma leakage 3, 1
• Hepatomegaly >2 cm is associated with severe disease 6

Severe Dengue (Requires Immediate ICU Care)

Severe dengue is defined by any of the following:

• Severe plasma leakage leading to shock (narrow pulse pressure ≤20 mmHg or hypotension) or fluid accumulation with respiratory distress 1, 7
• Severe bleeding requiring blood transfusion 1, 7
• Organ impairment including AST or ALT ≥1000 IU/L, impaired consciousness, or other organ failure 1, 6
• Dengue shock syndrome includes all criteria for dengue hemorrhagic fever plus hypotension or narrow pulse pressure 1

Laboratory Parameters for Risk Stratification

During First 4 Days of Illness (Febrile Phase)

• Platelet count is lower in patients who progress to severe disease (standardized mean difference -0.34) 4
• Thrombocytopenia <100,000/mm³ occurs in 77% of dengue patients, with rapidly declining counts predicting severe disease 5, 1
• Serum albumin is lower in those progressing to severe disease (standardized mean difference -0.5) 4
• Elevated transaminases (AST and ALT) during febrile phase predict severe disease (AST standardized mean difference 1.06; ALT 0.73) 4
• Hematocrit monitoring is essential—rising hematocrit indicates hemoconcentration from plasma leakage 3, 5
• Leukopenia (decreased TLC in 52.3% of patients) can indicate severe disease 5

Daily Monitoring Protocol

• Complete blood count daily to track platelet counts and hematocrit levels, which helps detect early signs of progression 3, 1
• Monitor trends rather than single values—a rapidly decreasing platelet count warrants hospitalization even if >100,000/mm³ 3

High-Risk Populations Requiring Lower Threshold for Hospitalization

Certain patient characteristics mandate more aggressive monitoring or hospitalization:

• Comorbidities including diabetes with hypertension (OR 2.16 for dengue hemorrhagic fever), heart disease, renal disease (OR 4.67), or immunocompromised states require hospitalization or very close monitoring 1, 4
• Age >60 years increases risk of complications 1
• Female patients have higher risk of severe dengue (OR 1.13) 4
• Pregnant women require mandatory hospitalization due to risk of maternal death, hemorrhage, preeclampsia, and vertical transmission 1
• Secondary dengue infections (versus primary) are associated with severe disease (OR 2.26; 95% CI 1.65-3.09) 4

Clinical Examination Findings

Definitive Prognostic Criteria for Severe Disease

Three clinical criteria definitively identify patients who will develop severe dengue (P < 0.001 for each):

• Abdominal pain 8
• Conjunctival injection 8
• Venipuncture site bleeding 8

When all three are present during the early febrile phase (day 0-3), they definitively predict severe dengue development 8

Additional Supportive Findings

• Positive tourniquet test significantly identifies progression to severe disease 8
• Petechiae predict severe dengue versus non-severe 8
• Hepatomegaly on examination suggests severe disease 8
• Bradycardia was observed in 46.15% of dengue patients 5

Diagnostic Testing to Confirm Dengue

• For symptoms ≤7 days: NAAT/PCR on serum is the preferred test, with NS1 antigen detection as an excellent alternative 2, 1
• For symptoms >7 days: IgM capture ELISA becomes the primary diagnostic test 1, 2
• Rapid diagnostic tests combining NS1 antigen and IgG have very high positive likelihood ratios and optimize management 1
• Document complete vaccination history to interpret serological results accurately due to cross-reactivity with other flaviviruses 2

Disease Course and Timing

• Dengue characteristically follows a triphasic course: febrile phase, critical phase (days 4-6 when severe disease develops), and recovery phase 7
• The incubation period is 4-8 days after mosquito exposure in endemic areas 2, 1
• The critical phase occurs 4-6 days after fever onset when plasma leakage and shock develop 8

Common Pitfalls to Avoid

• Never dismiss dengue based solely on absence of rash, as up to 50% of cases lack the characteristic exanthem 2
• Do not rely on single negative IgM test collected <7 days after onset, as this may reflect collection before antibody development 2
• Never use aspirin or NSAIDs when dengue cannot be excluded due to increased bleeding risk with thrombocytopenia 3, 1, 2
• Do not delay fluid resuscitation in patients showing signs of shock 3
• Avoid fluid overload, which can precipitate pulmonary edema or ARDS 3
• Never administer steroids, as they have been shown to have adverse effects in dengue management 3
• The absence of thrombocytopenia significantly reduces the probability of dengue, making it a useful rule-out finding 1