Dengue test in Nashik: which test to do, and on which day of fever

After the monsoon, many families in Nashik with a high fever ask the lab for "the dengue test" and get back a report with NS1, IgM, IgG and a blood count on it. Which one matters depends mostly on how many days the fever has lasted. A test done on the wrong day can come back negative even when the person has dengue. This guide explains what each test looks for, when it works best, and which results need a doctor the same day.

The short answer

• Days 1 to 5 of fever: the NS1 antigen test is the main test. Some labs also offer a PCR test.

• From about day 5 onwards: the IgM antibody test becomes the main test, because NS1 fades.

• On every day: a complete blood count (CBC) does not diagnose dengue, but it shows the platelet count and haematocrit that doctors use to judge how serious the illness is.

• A negative NS1 does not rule out dengue, especially if it was done late. Your doctor may repeat the test or add IgM.

What each dengue test looks for

• NS1 antigen. What it detects: a protein made by the dengue virus. Works best: days 1 to 5 of fever. What to know: can turn negative after the first week. ELISA tests done in a lab are more reliable than rapid card tests.

• RT-PCR. What it detects: the virus's genetic material. Works best: days 1 to 5 of fever. What to know: very accurate but not offered by every lab, and usually costs more.

• IgM antibody. What it detects: the body's early immune response. Works best: from about day 5. What to know: can stay positive for around 3 months, so it may reflect a recent earlier infection. It can occasionally react to other similar viruses.

• IgG antibody. What it detects: longer-lasting immunity. Works best: weeks after infection. What to know: a single IgG result cannot diagnose current dengue. It may mean a past infection.

• CBC (complete blood count). What it detects: platelets, haematocrit and white cells. Works best: every day of illness, as advised. What to know: not a dengue test. It is how doctors monitor the danger period.

India's national dengue programme bases testing on lab ELISA tests: NS1 early in the illness and IgM after about the fifth day. The US Centers for Disease Control and Prevention similarly recommends pairing an early test (NS1 or PCR) with an IgM test in the first week, and using IgM as the main test after day 7.

Which test on which day

Days 1 to 3. The virus is multiplying, and NS1 or PCR is most likely to be positive. IgM is usually still negative. A CBC gives the doctor a baseline to compare against later.

Days 4 to 5. This is an overlap period. NS1 may still be positive while IgM is starting to appear, so doing both together catches more cases.

After day 5. NS1 becomes less reliable, and IgM is the better test. By this stage, the CBC matters more than the diagnosis itself, because this is often the critical phase.

Count days from the first day of fever, not from the day you visit the doctor. Write the date down. It is the single most useful thing to tell the lab and the doctor.

Why a negative test does not always mean no dengue

A negative NS1 or PCR does not rule out dengue. The test may have been done too late, the virus level may have been low, or a rapid card may have missed it. In secondary dengue, where a person has had dengue before, NS1 can also be harder to detect.

If the fever, body ache, rash or falling platelets still fit dengue, your doctor may treat it as possible dengue anyway and repeat the test or add IgM. Doctors start care based on symptoms and the blood count, without waiting for a positive result.

The blood count: what the doctor is watching

The CBC is repeated because dengue can change quickly. Doctors look at two numbers together:

• Platelets, which help blood clot. A falling count is common in dengue.

• Haematocrit (HCT or PCV), which shows how concentrated the blood is. A rising haematocrit together with fast-falling platelets can mean fluid is leaking out of the blood vessels. This is a warning sign.

One low platelet number on its own does not decide treatment. For more on platelet counts, read Dengue fever platelet count: what families should know.

Warning signs: go to hospital the same day

The World Health Organization notes that severe dengue often appears just as the fever comes down, usually around days 3 to 7. Go to the emergency department straight away for:

• Severe stomach pain or vomiting that does not stop.

• Bleeding from the gums or nose, or blood in vomit or stool.

• Fast breathing, restlessness, extreme tiredness or confusion.

• Cold, pale or clammy skin, or passing very little urine.

Medicines while you wait for results

For fever and pain, paracetamol is usually used, at the dose your doctor advises. WHO advises avoiding painkillers such as ibuprofen and aspirin, because they can increase the risk of bleeding. Do not start antibiotics or steroids on your own, and keep drinking fluids unless a doctor tells you otherwise.

Getting tested in Nashik

• Get tested on a doctor's advice, so the right test is chosen for the day of fever.

• Ask whether the NS1 result is an ELISA or a rapid card test.

• Keep all reports together in date order and bring them to every visit. A trend tells the doctor far more than one report.

• Repeating NS1 every day is rarely useful. Repeating the CBC often is.

Questions people ask

Is the NS1 test enough? In the first few days it is the main test, but a negative result does not rule dengue out. After day 5, IgM is more useful.

My IgG is positive. Do I have dengue now? Not necessarily. IgG often shows a past infection. Your doctor will look at NS1, IgM, symptoms and the blood count together.

Can dengue be tested at home in Nashik? Many labs collect samples at home. The test is the same; what matters is that it is the right test for the day of fever and that a doctor reads the result.

Should the whole family be tested? Only those with symptoms. Dengue spreads through Aedes mosquitoes, not from person to person, so removing standing water around the home matters for everyone.

Talk to the doctor

Dr. Sumeet Mandale treats dengue and other seasonal fevers at Medinova Super Speciality Hospital, Mumbai Naka, Nashik. If you are unsure which test to do, or what a report means, call or WhatsApp +91 74476 86444. If any warning sign appears, go to the emergency department without waiting for results.

Read more: Dengue, Infectious disease diagnosis and treatment and Viral fever symptoms and warning signs.

Disclaimer

This guide is general information about dengue testing. It is not a diagnosis or a treatment plan for any one person. Test choice, medicines and the need for admission are decided by a doctor who has examined the patient.

References

• US Centers for Disease Control and Prevention. Clinical testing guidance for dengue.

• World Health Organization. Dengue and severe dengue.

• National Center for Vector Borne Diseases Control, Government of India. National guidelines for clinical management of dengue fever.