Dengue Duo (NS1 Antigen, IgG and IgM Antibody) Test

The Dengue Duo test is a combined diagnostic test used to detect current or past dengue virus infection by identifying both viral antigens and antibodies in the blood. It helps diagnose dengue fever early and differentiate between recent and past infections.

Components of the Dengue Duo Test:

1. NS1 Antigen
   • NS1 (Non-Structural Protein 1) is a viral protein produced by the dengue virus during early infection.
   • Detectable in blood from the first day of fever up to about 5–7 days.
   • Positive NS1 indicates an acute (early) dengue infection.
2. IgM Antibody
   • IgM is the first antibody produced by the immune system in response to dengue infection.
   • Detectable around 3–5 days after onset of symptoms and peaks within 2 weeks.
   • Presence of IgM suggests a recent dengue infection (acute or recent phase).
3. IgG Antibody
   • IgG appears later and remains in the blood for months to years after infection.
   • Indicates past dengue infection or secondary infection.
   • High IgG levels with or without IgM may suggest a secondary dengue infection, which can be more severe.

Purpose of the Dengue Duo Test:

• Early diagnosis of dengue fever by detecting NS1 antigen.
• Determine the stage of infection (early acute vs. recent vs. past infection).
• Identify primary vs. secondary dengue infection, which is important for prognosis.
• Guide clinical management and monitor outbreaks in endemic areas.

How the Test Works:

• Blood sample (usually serum or plasma) is tested using immunoassays or rapid test kits.
• NS1 antigen is detected by specific antibodies that bind the viral protein.
• IgM and IgG antibodies are detected by their binding to dengue antigens coated on the test device.

Clinical Significance:

• Early detection of NS1 helps start supportive care sooner to reduce complications.
• Antibody detection helps confirm infection if NS1 is negative or if testing is done late.
• Differentiating between primary and secondary infections helps predict severity risk.