Dengue Virus IgG

OVERVIEW

What is Dengue?

It is a viral infection which is transmitted into humans via mosquito (Aedes aegypti). Such mosquitos breed in tropical & subtropical climates & bear the virus in them, which is passed into humans when mosquito bites and sucks blood. There are 1- 4 serotypes (or types) of dengue virus namely DV-1, -2, -3, -4. Dengue occurs in majority of individuals who travel to endemic countries (i.e., having high prevalence of dengue cases). Most infected individuals show no symptoms, but some commonly seen initial symptoms include sudden high fever (40 degree C), severe headache, pain behind eyes/muscle or in joints, skin rash, nausea/vomiting, and other flu-like symptoms appearing after 4 or 7 days of being bitten.

What is dengue virus IgG lab test?

Dengue infection can be diagnosed in laboratory via detection of virus, viral nucleic acid, antigens (substance from outside body’s environment) or antibodies (substance produced by body’s immune system to fight infection). In this test we detect Immunoglobulin G antibody in blood released against dengue virus. IgG antibody is released after several weeks of infection but stays in the body for long time. 

Why is dengue virus IgG lab test done?

The test is done:

•             It helps in determining whether you have past or current dengue virus infection.

•             It aids in confirmation of dengue infection in patients who have a travel history and clinical symptoms.

•             When patients show flu-like symptoms and high grade fever characterized for dengue.

•             It helps when done in person already exposed to acute dengue infection. 

• Firstly, blood is drawn by inserting needle in vein in the arm/hand
• Blood sample collected in test tube or vial and sent to the laboratory
• The technician isolates serum from sample & performs Dengue virus IgG test, where it looks for presence or concentration of IgG antibody in it.

1. When must dengue blood test be taken?

If patient starts showing symptoms like fever, headache, muscle aches etc. and has travel history, then must get tested within 3 days of being infected.

2. Which test helps detect serotype of dengue?

PCR molecular testing helps detect virus genetic material in blood and determines which serotype from 4 are you infected with.

3. When does NS1 antigen test turn positive?

If person has been infected within 1 to 2 days and gets tested, then this test helps diagnose early infection.

4. Which test is conducted in dengue diagnosis before 5 days?

Before 5 days of infection; virus isolation in cell culture, NAAT (nucleic acid amplification test) or detection of viral antigens via ELISA is conducted.

5. How much platelets drop during dengue?

Normal platelets in body range from 1.5 to 4 lacs but drops to as low as 20,000 to 40,000 in the case of dengue patients.

NS1 antigen test is mostly recommended alongside IgM & IgG antibody test for proper diagnosis of early and late dengue infection.

INTERPRETATION OF THE RESULTS:

• Positive: Indicates presence of IgG antibodies in blood and confirms exposure to dengue infection sometime in the past. It means patient is now immune to that past DV infection and has antibodies to fight against it.
• Negative: Indicates absence of IgG antibody in blood, which means patient has not been exposed to dengue in the past and is at risk of getting DV infected.

You get tested for determining & confirming if person had past or has current dengue infection.