Dengue IgG and IgM Test: Understanding Dengue Diagnosis and Patient Care

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Table of Contents

Introduction

Dengue fever is a mosquito-borne viral disease that affects millions of people in tropical and subtropical regions every year. In countries like Bangladesh, dengue outbreaks have become a major public health challenge. Early detection and proper laboratory diagnosis save lives, reduce complications, and help prevent the widespread transmission of the virus. Among the diagnostic tools used for dengue infection, the Dengue IgM and IgG antibody tests play a critical role.

As a medical education and clinical service provider, HRTD Medical Institute aims to create awareness about laboratory diagnostics, infection prevention, and clinical evaluation. This article provides an extensive, easy-to-understand explanation of Dengue IgG and IgM tests: how they work, when they should be performed, what the results mean, and why reliable testing is crucial. Whether you are a student, patient, healthcare professional, or caregiver, this educational guide will help you understand the science and practice behind dengue diagnostics.

1. Understanding Dengue Fever

1.1 What is Dengue?

Dengue is caused by the Dengue virus (DENV), which belongs to the Flaviviridae family. There are four serotypes of dengue virus: DENV-1, DENV-2, DENV-3, and DENV-4. Infection by one serotype usually gives lifelong immunity against that serotype but not to the others. This is why individuals can be infected multiple times throughout their lifetime.

Common symptoms

Symptoms usually appear 4–10 days after a bite from an infected Aedes mosquito (Aedes aegypti or Aedes albopictus). The most common features include:

High fever (38.5° – 40°C)
Severe headache
Pain behind the eyes
Intense body aches, muscle pain, joint pain
Rash (appears after fever subsides in some cases)
Nausea or vomiting
Fatigue and weakness

Severe dengue (Dengue Hemorrhagic Fever or Dengue Shock Syndrome)

In some cases, dengue can progress to a life-threatening condition. Warning signs include:

Severe abdominal pain
Persistent vomiting
Bleeding gums or nose
Blood in stool or vomit
Rapid heartbeat or low blood pressure
Fluid accumulation (ascites, pleural effusion)

Early testing and medical attention reduce the risk of severe complications.

2. Role of Laboratory Diagnosis

Clinical symptoms alone cannot accurately diagnose dengue. Many tropical infections such as Chikungunya, COVID-19, malaria, typhoid, and viral fever share similar symptoms. Therefore, laboratory investigations are crucial.

Dengue diagnosis is broadly divided into two categories:

Detection of the virus itself
- Dengue NS1 Antigen Test
- PCR (Polymerase Chain Reaction)
Detection of antibodies made by the immune system
- Dengue IgM Test
- Dengue IgG Test

This article focuses on the second category: antibody-based tests.

3. Immunology Behind Dengue Infection

To understand the IgG and IgM tests, it is important to understand how the immune system responds to infection.

The body produces different types of antibodies depending on the stage of infection:

IgM (Immunoglobulin M): First response antibody. Appears a few days after infection.
IgG (Immunoglobulin G): Late and long-term antibody. Appears after IgM and remains in the body for years.

How antibodies work

After a virus enters the body:

Immune cells recognize the viral particles.
The body produces IgM to neutralize and fight the active infection.
Later, IgG antibodies form to provide long-term protection.

This pattern is used diagnostically:
IgM indicates recent or active infection.
IgG indicates past infection or immunity.

4. Dengue IgM Antibody Test

4.1 What is IgM?

IgM antibodies are the first immunoglobulins the body produces to fight a new infection. They appear quickly—usually within the first 3–5 days after the onset of symptoms.

Characteristics of IgM:

Large molecular size
Short duration in bloodstream
Strong early immune response

4.2 When is Dengue IgM detectable?

Usually positive from Day 5 onwards
Peaks around Days 10–14
May stay detectable for 2–3 months

Because IgM appears early, it is useful to diagnose recent infections, especially when NS1 antigen testing is unavailable or when the patient comes late.

4.3 What IgM positivity means

IgM Positive / IgG Negative → Primary recent dengue infection
IgM Positive / IgG Positive → Ongoing infection or secondary dengue

A positive IgM result usually confirms that the body is actively fighting dengue at the time of testing.

4.4 Limitations of IgM Testing

There are some challenges:

Very early (Days 1–3), IgM may be negative
Cross-reactivity with other flaviviruses (Zika, Yellow fever)
Cannot differentiate dengue serotype

Therefore, timing of testing is important.

5. Dengue IgG Antibody Test

5.1 What is IgG?

IgG antibodies appear later in the infection and stay long-term. They represent immune memory.

When do they appear?

Usually detectable from Day 7–14
Remain detectable for years or lifetime

5.2 What IgG positivity means

IgG Positive may indicate one of the following:

Past infection
— The patient previously had dengue and has developed immunity.
Secondary infection
— When people get dengue again with a different serotype, IgG increases quickly, even early in illness.
Late-stage active infection
— As IgM fades, IgG persists.

5.3 Importance of IgG Results

IgG helps doctors to understand:

Whether the infection is new or recurrent
Patient’s immune response status
Risk of severe dengue

Patients with secondary dengue sometimes experience worse complications, because the immune system responds aggressively (antibody-dependent enhancement).

6. Differences Between IgM and IgG Tests

Feature	IgM	IgG
Appearance	Early	Late
Time to detect	Day 4–5	Day 7–14
Duration	2–3 months	Years
Indicates	Recent infection	Past or secondary infection
Clinical value	Acute diagnosis	Immunity and risk assessment

Together, these tests help physicians understand when the infection occurred and how the body is responding.

7. When Should You Take a Dengue IgM or IgG Test?

Testing recommended under these conditions:

Fever lasting more than 3–5 days
Suspected mosquito bite exposure
Outbreak season
Severe symptoms or warning signs
Post-hospital follow-up

Appropriate timelines:

Days 0–5: NS1 Antigen test is best
Days 5–10: IgM is most useful
After Day 10: IgG may appear

Doctors often combine:

NS1 + IgM (For acute diagnosis)
IgM + IgG (For secondary infections)

8. How the Tests Are Performed

The Dengue IgM or IgG test is a blood-based immunoassay.

Sample Type

Venous blood collected from the arm

Methods Used

ELISA (Enzyme-Linked Immunosorbent Assay) – Gold standard
Rapid Test Kits (ICT) – Quick but less reliable

At HRTD Medical Institute, we prioritize laboratory and training methods based on accuracy, including ELISA-based testing and proper quality control.

9. Interpretation of Dengue IgM and IgG Test Results

Scenario 1: IgM Positive, IgG Negative

Indicates recent primary infection
Typically early-stage dengue

Scenario 2: IgM Positive, IgG Positive

Indicates active infection with secondary immune response
Possible second-time dengue

Scenario 3: IgM Negative, IgG Positive

Past infection or late-stage recovery
Patient may have immunity

Scenario 4: IgM Negative, IgG Negative

Very early infection
Or no dengue
Repeat test recommended after a few days

10. Why Dengue Antibody Tests Sometimes Show False Results

Causes of False Positives

Other flaviviruses (Zika, Japanese encephalitis)
Cross-reactive antibodies
Autoimmune diseases

Causes of False Negatives

Testing too early
Weak immune response
Lab variability

This is why HRTD Medical Institute emphasizes proper test timing, correct methodology, and interpretation by trained specialists.

11. Clinical Relevance of Dengue IgG and IgM

Laboratory diagnosis affects clinical decision-making:

11.1 Treatment decisions

Doctors use the test results to:

Plan fluid management
Determine hospitalization needs
Assess risk for shock or hemorrhage

11.2 Epidemiological monitoring

During outbreaks, antibody testing helps measure:

Community exposure
Infection patterns
Serotype spread

12. Patient Preparation and Precautions

Before testing

No fasting required
Inform doctors about medications
Report previous dengue episodes

After testing

Continue monitoring symptoms
Follow medical advice
Avoid self-medication

13. Why Early Diagnosis Saves Lives

Dengue mortality increases primarily from:

Late hospitalization
Inadequate fluid management
Misdiagnosis

Early IgM/IgG testing:

Reduces complications
Provides clinical direction
Prevents unnecessary treatments

14. Dengue Testing Services at HRTD Medical Institute

HRTD Medical Institute in Dhaka provides:

✔ State-of-the-art laboratory facilities

We use reliable, quality-controlled immunoassay methods for dengue IgM and IgG.

✔ Trained medical technologists

Our laboratory experts are professionally trained in sample handling and analysis.

✔ Affordable diagnostic services

We aim to make dengue testing accessible to all communities.

✔ Educational and training programs

We train healthcare workers and pathology students about dengue diagnostics, biosafety, and public health.

✔ Patient counseling

We help patients understand test results, follow-up, and preventive strategies.

Address:
HRTD Medical Institute
Section-6, Block-Kha, Road-1, Plot-11,
Metro Rail Pillar-249, Folpotti Mosque Lane,
Mirpur-10, Dhaka-1216

Contact:
01797522136, 01987073965, 01784572173

15. Frequently Asked Questions (FAQ)

1. Is the Dengue IgM test enough for diagnosis?

It helps confirm recent infection, but for a complete diagnosis, NS1 antigen or IgG comparison may be necessary.

2. Can IgM be negative but dengue still be present?

Yes. If you test too early (Days 1–3), IgM may be negative. NS1 or PCR is more useful at this time.

3. When should I repeat the test?

Repeat after 3–5 days if results are unclear and symptoms persist.

4. What is secondary dengue?

An infection by a different dengue serotype after a previous infection. Often more severe.

5. How long does IgG stay in the body?

Months to years, sometimes lifelong.

16. Prevention and Public Awareness

Testing is only one part of controlling dengue. Communities should practice prevention:

Mosquito control

Remove stagnant water
Clean rooftop tanks and flowerpots
Use mosquito nets and repellents

Personal awareness

Avoid mosquito-prone areas at dawn/dusk
Seek testing early
Do not take painkillers like aspirin or ibuprofen without medical advice

17. Summary

Dengue is a life-threatening disease requiring timely and accurate diagnosis. The Dengue IgM Test helps determine recent infection, while the Dengue IgG Test assesses past or secondary infection. Proper interpretation of these tests guides doctors in treatment, hospitalization decisions, and complication prevention.

At HRTD Medical Institute, we are committed to providing:

Accurate laboratory diagnostics
Medical training & technical education
Patient-centered guidance and affordability

By educating patients and future health professionals, we aim to reduce dengue-related morbidity and mortality in Bangladesh.