Dengue Fever Test

What is a Dengue Fever Test?

A Dengue Fever Test is a group of blood tests that detects or helps confirm an infection caused by the dengue virus. Dengue is a viral infection, that is transmitted by the bite of infected Aedes mosquitoes. 

The virus can cause fever, headache, pain behind the eyes, body aches, nausea or skin rash. These symptoms sometimes look similar to flu, malaria, chikungunya and other infections. This blood test helps investigate if dengue is the actual cause behind the symptoms or not.

Different types of dengue tests may look for different markers of infection, including virus’s genetic material, the NS1 antigen or antibodies produced by the immune system. It depends on how long a person has had symptoms and timing of the illness. 

Molecular and antigen tests are considered more useful during the early stage of infection, whereas antibody testing may be recommended when the immune response develops.

A dengue test may be recommended when symptoms and medical history suggest dengue or when there has been possible exposure in an area where dengue is circulating. 

In some people, dengue can develop into a severe illness that requires urgent medical care.

Symptoms That Indicate Dengue Test is Required

Person’s symptoms, travel or residence, and previous dengue infection history are considered before recommending the test.

Symptoms may include:

• Sudden high fever
• Severe headache
• Pain behind the eyes
• Muscle, bone, or joint pain
• Nausea or vomiting
• Skin rash
• Mild bleeding from the nose or gums
• Easy bruising
• Unusual tiredness or weakness

Dengue symptoms can show up a few days after a mosquito bite. Often, mild cases recover within one to two weeks. 

Dengue can become a serious condition. If you have severe or ongoing stomach pain, cannot stop vomiting, notice blood in your vomit or stool or have a bleeding nose or gums, do not wait; instead, seek immediate medical attention. If you are feeling unusually weak, restless, very sleepy, short of breath, or cold and clammy, go to an emergency department or contact a healthcare professional immediately.

Types of Dengue Fever Tests

• Dengue NS1 Antigen Test: This test detects the NS1 protein released into the blood by the dengue virus. It helps the most in the first week after you start feeling sick. 
• Dengue RT-PCR Test: This molecular test detects genetic material of the virus (RT-PCR). It helps doctors to know whether a patient has dengue fever and performs well in the first week of symptoms. 
• Dengue IgM Antibody Test: If the symptoms have been present for a few days, it looks for IgM antibodies from the immune system and indicates a recent infection. 
• Dengue IgG Antibody Test: To detect past exposure. IgG test is not usually recommended for diagnosis of an acute infection. A positive IgG test does not always indicate that the cause of current illness is dengue, either.

The clinician selects the test based on timing of symptoms, exposure, prior dengue infection, and local testing guidelines.

Preparation & Sample Collection for Dengue Test

Preparation

• Fasting is usually not required.
• Tell your doctor when your symptoms first appeared and if you have ever had dengue.
• If dengue is prevalent in your area of residency or you have travelled recently, your care provider should be aware of it.
• Follow your doctor’s recommendations and let them know about any medications or supplements you are using.

Sample Collection

Blood sample is collected in the sample tube by inserting a sterile needle into a vein. 

The procedure usually takes only a few minutes. You may experience brief discomfort or mild bruising at the collection site.

Lab Results & Tests
In the laboratory a blood sample is tested by one or more methods to look for evidence of dengue infection.
The lab looks for specific markers that will tell if the dengue virus is in the body.

• Dengue Virus RNA: The genetic material of the virus detected by the molecular tests like Dengue RT-PCR Test. If the test is positive, it indicates you have an active infection.
• NS1 Antigen: If NS1 antigen test is positive, it means that a protein released by the virus is present in the body and there may be an ongoing dengue infection. NS1 negative does not rule out virus, additional investigation may require.
• IgM Antibodies: If IgM antibodies are present, it means the person had dengue fever recently. Viruses such as Zika or West Nile could affect the results. 
• IgG Antibodies: It may indicate a past infection or a later-stage infection. 

There is no normal range for the dengue fever test; it is generally interpreted as: 

• Positive
• Negative 
• Uncertain/Indeterminate 

“The reference ranges or result indicators, tend to vary with the laboratory and the methodology used. People should talk to their health care provider for proper interpretation of the results.”

Understanding Negative Results

The absence of dengue virus RNA or NS1 antigen in the sample is often indicated by negative results for molecular or antigen testing.

For antibody testing, interpretation depends on whether IgM or IgG antibodies are detected and on the timing of sample collection relative to symptoms’ beginning. 

A negative result does not always completely rule out dengue, particularly if testing is performed very early or late in the illness. Your healthcare provider may recommend repeat or additional testing or testing for other infections when clinically appropriate.

What To Do If You Test Positive for Dengue
If your dengue test is positive, your doctor will work with you to develop an individualised treatment plan that helps to manage and control your symptoms and prevent complications. They might tell you to get plenty of bed rest, take plenty of fluids, watch for any worsening symptoms, and take any medications exactly as prescribed.

Aspirin or NSAIDs might increase the risk of bleeding in dengue patients. Therefore, always follow your doctor’s advice for a safe and smooth recovery.

Your healthcare provider may recommend additional investigations based on your symptoms and test results, 

• Complete Blood Count (CBC)
• Platelet Count
• Hematocrit Test
• Dengue NS1 Antigen Test
• Dengue IgM Antibody Test
• Dengue IgG Antibody Test
• Dengue PCR Test
• Liver Function Tests
• Electrolyte Tests

These tests provide supporting information. They cannot replace a dengue-specific test. A treatment plan and additional investigations suggested by a doctor are based on your symptoms and history.

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