Dengue NS1 Antigen
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Category
Blood
Sample
Blood
Report Time
4 hrs
Fasting
Not needed
About Dengue NS1 Antigen
This combined test panel is used to diagnose dengue fever, a mosquito-borne viral infection common in tropical and subtropical regions, by detecting the virus and the body's immune response to it at different stages of illness.
The NS1 antigen is a viral protein that appears in the blood very early in infection, often detectable from the first day of fever through about day five, making it the most useful marker for early diagnosis.
As the infection progresses, the immune system begins producing IgM antibodies (typically detectable from around day 4 or 5 onward, indicating a recent or current infection) and later IgG antibodies, which persist for years and indicate past exposure or, in a secondary infection, can appear more quickly and at higher levels.
Testing all three markers together significantly improves diagnostic accuracy across the full timeline of illness, since relying on just one marker can miss infections detected outside its specific window.
When Should You Get This Test?
This test is recommended if you have:
- High fever with a severe headache, especially behind the eyes
- Severe joint and muscle pain (sometimes called 'breakbone fever')
- A skin rash appearing a few days into the illness
- Recent travel to or residence in a dengue-endemic area
- Unexplained bruising or bleeding gums during a febrile illness
Conditions This Test Can Detect
This panel confirms:
- Acute dengue infection, primarily through NS1 antigen and early IgM
- Recent past dengue infection, through IgG antibodies
- Whether the infection is a first-time (primary) or repeat (secondary) dengue infection, which affects the risk of severe complications
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How to Prepare
- No fasting is required for this test.
- Testing is ideally done within the first 5 days of fever onset for the most reliable NS1 antigen detection.
- If the first test is negative but symptoms persist, your doctor may recommend repeat testing a few days later to catch a later-appearing antibody response.
Normal Reference Ranges
Results are reported as reactive (positive) or non-reactive (negative) rather than as a numeric value.
| Parameter | Normal Range |
|---|---|
| NS1 Antigen | Non-reactive (negative) |
| IgM Antibody | Non-reactive (negative) |
| IgG Antibody | Non-reactive (negative) |
A positive NS1 antigen confirms active, current infection, while positive IgM suggests recent infection and positive IgG alone (without NS1 or IgM) generally indicates infection at some point in the past.
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Frequently Asked Questions
When is the best time to test after fever starts?
NS1 antigen is most reliable within the first 5 days of fever, while IgM antibodies become more detectable from day 4 or 5 onward — testing too early or too late in the illness can affect which markers show up positive.
What does a positive IgG alone mean?
If NS1 and IgM are negative but IgG is positive, it usually indicates a past dengue infection rather than a current one.
Is a repeat test ever needed?
Yes, if initial results are negative but dengue is still strongly suspected based on symptoms, your doctor may recommend repeating the test a few days later as antibody levels rise.
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Medical Disclaimer: This page is for informational purposes only and does not constitute medical advice. Lab test results should always be interpreted by a qualified healthcare professional in the context of your clinical history. Do not self-diagnose or alter your treatment based on test results alone.
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