Dengue Test: Types, Normal Range, Symptoms & Complete Guide

Dengue Test: Types, Purpose, Results, Symptoms & Complete Guide

Overview

The Dengue Test is a diagnostic test used to detect the presence of the dengue virus or the body’s immune response to it. Dengue is a viral infection transmitted by the bite of an infected Aedes aegypti mosquito, a species commonly found in tropical and subtropical areas. Although many dengue cases are mild, some can progress to more serious conditions such as dengue hemorrhagic fever and dengue shock syndrome. Early diagnosis plays a key role in preventing complications and starting the right treatment at the right time.

Doctors use dengue tests to confirm whether an infection is present, to identify the stage of infection, and to decide how treatment and monitoring should continue. Because early symptoms can look similar to malaria, typhoid, chikungunya, and even seasonal flu, laboratory testing becomes essential for accurate diagnosis.

What Is a Dengue Test?

A dengue test helps detect either the dengue virus itself or the immune system’s response to the virus. The test looks for three different markers:

• Viral proteins (antigens)
• Immune antibodies (IgM and IgG)
• Viral genetic material (RNA)

These markers appear at different stages of the infection, making it possible for doctors to determine whether the infection is new, active, recent, or part of a previous dengue episode.

Main Types of Dengue Tests

There are three major categories of dengue tests used worldwide:

NS1 Antigen Test

• Detects the NS1 protein released by the dengue virus
• Best for early diagnosis, especially during Day 1–7 of fever
• Useful when the immune system has not yet produced antibodies
• Helps confirm dengue before complications begin

IgM/IgG Antibody Test

• IgM antibodies appear around Day 4–5
• IgG antibodies appear later and may remain for months or years
• IgM indicates current or recent infection
• IgG indicates past infection or secondary dengue

PCR (RT-PCR) Test

• Detects dengue viral RNA
• Extremely accurate
• Mainly used during the early or acute stage of infection
• Helps identify the specific dengue serotype

These tests together help identify the stage and severity of dengue.

How Dengue Develops in the Body

The dengue virus does not originate inside the body. It enters when an infected Aedes mosquito bites a person. After entry:

1. The virus travels through the bloodstream.
2. It multiplies quickly in blood cells and tissues.
3. Viral proteins such as NS1 antigen appear in the blood.
4. The immune system begins producing IgM and IgG antibodies to fight the virus.

Dengue tests detect either these viral components or the immune response, helping determine how far the infection has progressed.

Types of Dengue Tests and Their Role

1. NS1 Antigen Test (Early Detection)

This test is especially valuable during the first week of fever. It detects the viral protein NS1, which appears even before antibodies develop. NS1 provides the earliest confirmation of dengue and helps doctors start monitoring platelet levels and fluid balance from the beginning.

2. IgM Antibody Test (Recent Infection)

IgM antibodies begin to rise around Day 4–5 of the illness. A positive IgM result generally indicates a recent or ongoing dengue infection. This test is often used when the NS1 test becomes negative during the later days of fever.

3. IgG Antibody Test (Past or Secondary Infection)

IgG antibodies appear later than IgM and can remain in the body for a long time. A positive IgG result signals a past infection or a secondary dengue episode. Secondary dengue is considered more severe, making IgG testing very important.

4. PCR (RT-PCR) Test (Highly Accurate)

PCR testing directly detects dengue virus RNA. It is highly sensitive and specific. This test is especially useful during the early phase of fever or when doctors need confirmation for severe, complicated, or high-risk cases.

Main Functions and Importance of Dengue Test

1. Confirms Dengue Infection

Dengue shares symptoms with malaria, typhoid, chikungunya, and viral fever. Laboratory tests ensure that treatment is accurate and timely.

2. Identifies the Stage of the Disease

• NS1 = early infection
• IgM = recent or active infection
• IgG = past infection or secondary dengue

This helps doctors understand the timeline and progression of the illness.

3. Detects Past or Secondary Dengue

Secondary dengue infections can be more severe. IgG tests help identify these cases early.

4. Prevents Serious Complications

Early testing allows the medical team to monitor:

• Platelet count
• Fluid levels
• Blood pressure

This helps prevent:

• Dengue hemorrhagic fever
• Dengue shock syndrome

5. Useful in Outbreak Situations

Dengue tests help detect clusters of infection. Public health authorities use this information to control mosquito breeding and spread.

Causes of Low or Negative Dengue Test Results

A dengue test may show negative results in the following situations:

• The person does not have dengue
• The test was taken very early, before NS1 or antibodies appear
• Antibody levels are too low
• Viral load is low during sample collection
• Rare laboratory errors

Negative results may still require repeat testing if symptoms continue.

Symptoms When Dengue Test Is Low or Negative

If the result is truly negative, the person usually does not have dengue. However, if the test was taken too early, symptoms may still include:

• High fever
• Headache
• Joint or muscle pain
• Weakness
• Tiredness

In such cases, doctors often recommend repeating the test after 24–48 hours for accurate diagnosis.

Causes of High or Positive Dengue Results

A positive result typically means:

• NS1 Positive: Early active dengue
• IgM Positive: Recent or current infection
• IgG Positive: Past infection or secondary dengue
• PCR Positive: Viral RNA detected, confirming active infection

Symptoms of High or Positive Dengue Results

Common Symptoms

• Sudden high fever
• Severe headache
• Pain behind the eyes
• Intense muscle and joint pain (often called “breakbone fever”)
• Nausea or vomiting
• Rashes on skin
• Extreme tiredness

Severe Symptoms

These may indicate complications and require urgent medical attention:

• Bleeding gums or nose
• Severe stomach pain
• Blood in vomit or stool
• Difficulty breathing
• Low blood pressure
• Feeling faint or confused

Reference Ranges

Sample Type

• Blood sample
• Serum or plasma commonly used
• PCR typically requires plasma during early infection

Test Preparation

• No fasting required
• Regular medicines can be continued unless doctor says otherwise
• Stay hydrated for easier blood collection
• Inform the doctor about the exact day the fever started
• Early-day information helps choose the correct test (NS1 or antibody tests)

When to Consult a Doctor

You should seek medical help if you experience:

Early Symptoms

• High fever for 2–3 days
• Severe headache
• Pain behind the eyes
• Body and joint pain
• Fatigue or weakness

Warning Signs

• Continuous vomiting
• Red spots or skin rashes
• Bleeding from gums or nose
• Sudden drop in platelets
• Dizziness or low blood pressure

Emergency Symptoms

Go to the hospital immediately if you have:

• Severe abdominal pain
• Persistent vomiting
• Blood in stool or vomit
• Difficulty breathing
• Feeling faint, confused, or extremely weak

Important Word Explanations

• NS1 Antigen: A viral protein released early in dengue infection
• IgM Antibody: Immune protein indicating recent dengue infection
• IgG Antibody: Immune protein indicating past or secondary infection
• PCR: Test detecting dengue virus genetic material
• Secondary Dengue: Dengue infection occurring again in the same person
• Hemorrhagic Fever: Severe dengue that leads to bleeding

~END~