Dengue IgG Positive, IgM Negative, NS1 Negative: Interpretation and Management
This serologic pattern indicates past dengue infection, not acute disease, and requires no specific dengue treatment. 1, 2
Clinical Interpretation
This combination of results has a clear diagnostic meaning:
IgG positive with IgM and NS1 negative definitively indicates prior dengue exposure, not current acute infection. 1, 2 IgG antibodies persist for months to years after the initial infection, serving as markers of previous exposure. 3, 1
The negative NS1 rules out acute infection because NS1 antigen is detectable from day 1 through day 10 of illness, with peak sensitivity (75-90%) during days 1-5. 1, 4 If the patient were acutely infected, NS1 would be positive during this window. 3, 1
The negative IgM further confirms this is not recent infection because IgM appears 3-5 days after symptom onset and remains detectable for 2-3 months. 3, 1 The absence of IgM indicates the infection occurred beyond this 2-3 month window. 3
Management Recommendations
No dengue-specific treatment is indicated for this patient. 1, 2 However, proceed with the following algorithm:
If the Patient is Currently Symptomatic with Fever:
Investigate alternative diagnoses because this pattern excludes acute dengue as the cause of current symptoms. 3, 1 The positive IgG simply reflects past exposure, not active disease. 2, 5
Consider testing for other febrile illnesses endemic to the patient's exposure area, including malaria, typhoid, leptospirosis, or other flaviviruses like Zika. 3
If Definitive Confirmation is Needed:
Perform plaque reduction neutralization testing (PRNT) if you need to distinguish dengue from other flavivirus infections (Zika, yellow fever, Japanese encephalitis), as IgG antibodies cross-react among flaviviruses. 3, 5
PRNT titer ≥10 for dengue with <10 for other flaviviruses confirms past dengue infection specifically. 3, 1, 5 However, PRNT is typically only available through public health laboratories or CDC. 3
If the Patient is Asymptomatic:
- No further testing or treatment is required. 2, 5 Document the positive IgG as evidence of prior dengue immunity. 2
Critical Pitfalls to Avoid
Do not treat this as acute dengue infection. The absence of both NS1 and IgM definitively excludes acute disease. 3, 1 Treating based on IgG alone would be inappropriate. 2
Do not assume the timing of past infection from IgG alone, as these antibodies persist indefinitely. 1, 2 The specific timing cannot be determined from serology. 3, 1
Be aware of flavivirus cross-reactivity. If the patient has travel history to areas with multiple flaviviruses or has received yellow fever or Japanese encephalitis vaccination, the positive IgG may reflect those exposures rather than dengue. 3, 5 Consider PRNT if this distinction matters clinically. 3, 5
Do not repeat dengue serologic testing unless the patient develops new symptoms consistent with acute dengue, in which case test with NS1/NAAT and IgM if within 7 days of new symptom onset. 3, 1