Dengue Test (NS1, IgM, IgG)

The three dengue tests explained

Dengue diagnosis depends on when you test after symptoms start. Different tests are positive at different times:

What does a POSITIVE NS1 mean?

What does POSITIVE IgM mean?

What does POSITIVE IgG mean?

Platelet count in dengue: when is it dangerous?

Warning signs: go to hospital immediately if you have:

• Severe abdominal pain or tenderness
• Persistent vomiting (more than 3 times in 24 hours)
• Bleeding from gums, nose or in urine/stools
• Sudden drop in temperature (below 38°C) after days of high fever
• Feeling cold, clammy or confused (shock)

NS1 vs IgM vs IgG vs platelet count: how they compare

“Dengue test” is several tests, and the right one depends on which day of the fever it is:

Day of fever decides the test: NS1 early, antibodies later. A negative test on the wrong day proves nothing.

Reading your report: what your doctor actually looks at

When a doctor opens a dengue result, the number itself is only the starting point. Here is the checklist they run through — and the same checklist helps you read your own report calmly:

1. Which day of fever? NS1 is for days 1–5, IgM from day 5 on. A negative NS1 on day 7 or a negative IgM on day 3 is expected, not reassuring — match the test to the day.
2. What is the platelet trend? A falling platelet count across daily CBCs matters more than any single value. Bring every report so the slope is visible.
3. Any warning signs? Severe abdominal pain, persistent vomiting, bleeding, extreme fatigue or restlessness are warning signs that need prompt medical care regardless of test results.
4. Which infection is it? IgG alongside IgM suggests secondary dengue, which carries higher risk of severe disease — worth knowing, not worth panicking over.
5. What is the haematocrit doing? A rising haematocrit with falling platelets suggests plasma leakage — the pattern doctors watch most closely in hospital.

Dengue is managed by monitoring, not by a single test result — daily platelet counts and warning-sign watch matter more than any one report. Discuss the full picture with your doctor, and seek prompt care for warning signs.

Dengue test price in India: typical bands across major lab chains

Dengue panels bundle the antigen and antibody tests; standalone NS1 or antibody tests cost less. Typical list-price bands:

These are approximate bands, not quotes: prices change often and vary by city, and home collection can add a small fee. Where possible, choose a NABL-accredited lab, and remember the reference range printed on your own report is the one that counts.

Frequently Asked Questions

Pharmacist's practical notes

Timing is the whole game in dengue testing: NS1 in the first five days, antibodies after. The commonest error is a single test on the wrong day being read as an answer — a negative NS1 on day 8 or a negative IgM on day 2 means the test was mistimed, not that dengue is excluded. When in doubt, the test is repeated at the right interval.

Avoid NSAID painkillers (ibuprofen, diclofenac and similar) during suspected dengue — they raise bleeding risk when platelets are falling. Paracetamol is the usual choice for fever, at standard doses, but confirm with your doctor. And platelet counts are for monitoring trends, not for transfusing to a number — transfusion decisions are clinical, not arithmetic.

In India

Indian labs offer NS1, IgM/IgG and combo panels. Dengue testing typically costs &rupee;600–&rupee;1,200, though prices vary by city and lab; rapid card tests cost less but are less reliable than lab-based ELISA.

Where possible, choose a NABL-accredited lab. During outbreaks, home collection from a reputable chain keeps a feverish patient out of crowded waiting rooms.

References

Sources cited on this page. PubMed links open the original abstract.

1. Guzman MG, Halstead SB, Artsob H, et al. Dengue: a continuing global threat. Nat Rev Microbiol. 2010;8(12 Suppl):S7–16. PMID 21079655 · doi:10.1038/nrmicro2460
2. Lima MRQ, Nunes PCG, Dos Santos FB. Serological Diagnosis of Dengue. Methods Mol Biol. 2022;2409:173–196. PMID 34709642 · doi:10.1007/978-1-0716-1879-0_12
3. Versiani AF, Martins EM, Ferreira LCS, et al. Performance of VIDAS Diagnostic Tests for the Automated Detection of Dengue Virus NS1 Antigen and of Anti-Dengue Virus IgM and IgG Antibodies. Diagnostics (Basel). 2023;13(6):1137. PMID 36980445 · doi:10.3390/diagnostics13061137

NS1 antigen, IgM, and IgG, three dengue tests and when to use each

Dengue testing uses three distinct markers that are relevant at different stages of infection:

• NS1 antigen (non-structural protein 1): The dengue virus produces NS1 protein in large quantities during active replication. NS1 is detectable in blood from day 1 to day 9 of illness, before the immune response fully develops. It is the best test in the first five days. A positive NS1 confirms active dengue infection. Sensitivity is around 80–90% in primary infection but lower in secondary infection (when pre-existing antibodies clear NS1 faster).
• Dengue IgM: The immune system begins producing IgM antibodies from day 4–5 of illness, peaking at weeks 2–3 and remaining detectable for 2–3 months. IgM confirms dengue if the patient presents late (after day 5). It can cross-react with Zika virus and other flaviviruses, so a positive result must be interpreted alongside clinical context and travel history.²
• Dengue IgG: IgG appears slightly later than IgM and remains detectable for years. A rising IgG titre between acute and convalescent samples (taken 2 weeks apart) confirms recent infection. High IgG early in illness indicates secondary dengue, a second dengue infection with a different serotype, which carries significantly higher risk of dengue haemorrhagic fever.

Dengue haemorrhagic fever and the warning signs

Most dengue infections cause a self-limiting flu-like illness (dengue fever): high fever, severe headache, pain behind the eyes, joint and muscle pain ("breakbone fever"), and a rash. However, a minority, especially secondary infections or young children, progress to severe dengue (dengue haemorrhagic fever or dengue shock syndrome), which can be life-threatening.

Warning signs that mandate urgent hospital assessment (WHO criteria):

• Abdominal pain or tenderness
• Persistent vomiting (inability to keep fluids down)
• Clinical fluid accumulation (ascites, pleural effusion)
• Mucosal bleeding (nosebleed, gum bleeding, blood in vomit or stool)
• Lethargy, restlessness, or rapid deterioration
• Liver enlargement above 2 cm
• Platelets falling rapidly below 100 × 10⁹/L or haematocrit rising (indicating plasma leakage)

During the critical phase (days 3–7 of illness, when fever may actually break), platelets and haematocrit must be monitored daily, or twice daily in severe cases. Dengue has no specific antiviral treatment; management is supportive with careful fluid balance and close monitoring for haemorrhage.

What full blood count findings suggest dengue

Before NS1 or antibody testing is available, the FBC provides important clues. Characteristic findings in dengue include: leucopenia (low white cell count, often below 4 × 10⁹/L by day 3), thrombocytopenia (low platelets, often falling progressively, a platelet count below 100 is a warning sign; below 20 risks spontaneous bleeding), and a rising haematocrit (concentration of red cells) indicating haemoconcentration from plasma leakage. These FBC changes in a febrile traveller returning from a dengue-endemic region should prompt specific dengue testing immediately.