Dengue IgG Serology: Interpretation and Diagnostic Approach

Clinical Interpretation of Positive IgG Results

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, 2
IgG antibodies can persist for months to years after infection, so its presence alone does not indicate acute disease. 1, 3
IgG alone without IgM or positive NAAT in symptomatic patients suggests past infection, not acute disease. 1, 2

For symptomatic patients ≤7 days from symptom onset: Perform dengue NAAT (or NS1 antigen test) plus IgM testing. 1, 2
For symptomatic patients >7 days from symptom onset: Perform IgM antibody testing. 1, 2
When both IgM and IgG are positive, this suggests recent or current dengue infection. 1, 2
When both IgM and IgG are positive, confirmatory PRNT testing should be performed against dengue, Zika, and other endemic flaviviruses if definitive diagnosis is needed for clinical management. 1, 4
Negative IgG does not exclude acute infection if tested early in the disease course. 1, 4

PRNT titer ≥10 for dengue with negative Zika PRNT (<10) confirms recent dengue infection. 2, 5
PRNT titer ≥10 for both dengue and Zika indicates flavivirus infection but cannot identify the specific virus without additional clinical and epidemiologic data. 2, 5
PRNT should be considered when: definitive diagnosis affects clinical management, patient is pregnant, distinguishing dengue from Zika is clinically important, or results will guide epidemiologic investigation. 1, 2, 3, 4

Dengue IgG can cross-react with other flaviviruses (Zika, yellow fever, Japanese encephalitis). 1, 3
If both dengue and Zika IgG are positive, or if definitive diagnosis is needed, perform PRNT to identify the specific infecting virus. 1, 2
IgG antibodies persist for months to years, making it impossible to determine when infection occurred based on serology alone; clinical and epidemiologic data (travel history, local transmission patterns) must guide interpretation. 1, 3
In endemic areas with co-circulating flaviviruses, interpretation requires consideration of local epidemiology. 1, 3

For pregnant women, the same interpretation applies, but timing of infection relative to pregnancy cannot be determined by serology alone and requires clinical correlation. 3