What are the recommendations for someone with a positive Dengue (Dengue virus) Immunoglobulin G (IgG) test?

Dengue IgG Positive Test: Clinical Interpretation and Management

A positive Dengue IgG test indicates past dengue virus infection and does not require specific treatment, but the result must be interpreted in the clinical context—particularly whether the patient is symptomatic or asymptomatic—and may require confirmatory testing with plaque reduction neutralization test (PRNT) to distinguish from other flavivirus infections. 1

Clinical Context Determines Next Steps

For Symptomatic Patients with Positive IgG

If the patient has a clinically compatible illness:

• Timing matters critically: IgG alone without IgM or positive NAAT suggests past infection, not acute disease 1
• Perform additional testing to determine if this is an acute infection:
  • If ≤7 days from symptom onset: Perform dengue NAAT (or NS1 antigen test) plus IgM testing 1
  • If >7 days from symptom onset: Perform IgM antibody testing 1
• IgG can persist for months to years after infection, so its presence alone does not indicate acute disease 1

When both IgM and IgG are positive:

• This suggests recent or current dengue infection 1
• Confirmatory PRNT testing should be performed against dengue, Zika, and other endemic flaviviruses if definitive diagnosis is needed for clinical management 1
• PRNT titer ≥10 for dengue with negative Zika PRNT (<10) confirms recent dengue infection 1

For Asymptomatic Patients with Positive IgG

The primary clinical significance is for vaccination screening:

• Positive IgG indicates prior dengue exposure, which is the required criterion for CYD-TDV (Dengvaxia) vaccination 2
• Dengue IgG rapid diagnostic tests demonstrate 95.3% sensitivity and 98.0% specificity for determining serostatus for prevaccination screening 2
• Vaccination is only recommended in dengue-seropositive individuals aged ≥9 years, as seronegative vaccinees have increased risk of severe dengue upon subsequent infection 2

Critical Interpretation Pitfalls

Cross-Reactivity with Other Flaviviruses

• Dengue IgG can cross-react with other flaviviruses (Zika, yellow fever, Japanese encephalitis) 1
• If both dengue and Zika IgG are positive, or if definitive diagnosis is needed, perform PRNT to identify the specific infecting virus 1
• PRNT titer ≥10 for both dengue and Zika indicates flavivirus infection but cannot identify the specific virus without additional clinical and epidemiologic data 1

Cannot Determine Timing of Infection

• IgG antibodies persist for months to years, making it impossible to determine when infection occurred based on serology alone 1
• Clinical and epidemiologic data (travel history, local transmission patterns) must guide interpretation 1

Practical Management Algorithm

Step 1: Assess clinical status

• Symptomatic → Proceed to Step 2
• Asymptomatic → Document prior dengue exposure; eligible for Dengvaxia if age ≥9 years 2

Step 2: For symptomatic patients, determine timing

• ≤7 days from symptom onset → NAAT/NS1 + IgM testing 1

• 7 days from symptom onset → IgM testing 1

Step 3: Interpret combined results

• IgG+ alone = Past infection, not acute 1
• IgG+ and IgM+ = Recent/current infection; consider PRNT if definitive diagnosis needed 1
• IgG+ and NAAT+ = Acute infection; perform PRNT for confirmation 1

Step 4: Consider PRNT when:

• Definitive diagnosis affects clinical management 1
• Patient is pregnant 1
• Distinguishing dengue from Zika is clinically important 1
• Results will guide epidemiologic investigation 1

Key Clinical Caveats

• Negative IgG does not exclude acute infection if tested early in the disease course 1
• In endemic areas with co-circulating flaviviruses, interpretation requires consideration of local epidemiology 1
• For pregnant women, the same interpretation applies, but timing of infection relative to pregnancy cannot be determined by serology alone and requires clinical correlation 1
• Rapid diagnostic tests for IgG show good performance (sensitivity 80-100%) but are optimized for secondary infections and convalescent samples 3