What is Dengue Virus Antibody - IgG IgM ELISA?
Also Known As:
Dengue Fever Antibodies, Dengue Fever Virus
Dengue Antibodies (IgG, IgM)|Dengue Virus by PCR
Dengue fever is a viral infection transmitted to humans by mosquitoes that live in tropical and subtropical climates and carry the virus. Blood testing detects the dengue virus or antibodies produced in response to dengue infection.
According to the Centers for Disease Control and Prevention (CDC), dengue infections have been reported in more than 100 countries from parts of Africa, the Americas, the Caribbean, the Eastern Mediterranean, Southeast Asia, and the Western Pacific. It is a fast emerging infectious disease, according to the World Health Organization (WHO), with an increasing number of cases and countries affected throughout the world. The actual number is not known because about 75% of cases are asymptomatic, but a recent estimate put the number of annual dengue infections as high as 390 million. Approximately 50 to 100 million symptomatic cases occur annually worldwide.
In the U.S., the majority of dengue cases occur in travelers returning from areas where dengue is endemic. Most dengue cases in U.S. citizens occur in people who live in Puerto Rico, the U.S. Virgin Islands, Samoa, and Guam. Outbreaks, where a large number of cases occur in a defined area, are rare in the U.S. In recent years, there have been small outbreaks in Texas and Hawaii and a few cases diagnosed in southern Florida.
Many individuals will develop no symptoms at all, or have only a mild illness when exposed to one of the four serotypes (1-4) of the dengue virus. For those who do develop symptoms, the prognosis is still very good for full recovery within a few weeks. The most common initial symptoms are a sudden high fever (104°F or 40°C) and flu-like symptoms that appear roughly 4 to 7 days after being bitten by an infected mosquito (this is called the incubation period and can range from 3 to 14 days). Additional signs and symptoms may include severe headache, especially behind the eyes, muscle and joint pain, skin rash, nausea, vomiting, and swollen glands.
Some people who develop a fever will recover on their own with no lasting ill effects while others may progress to severe dengue fever (sometimes called Dengue Hemorrhagic Fever). If the disease progresses to this form, a new wave of symptoms will appear 3 to 7 days after initial symptoms and as the fever recedes. These may include nose bleeds, vomiting blood, passing blood in the stool, difficulty breathing, and cold clammy skin, especially in the extremities. During the second phase, the virus may attack blood vessels (the vascular system), causing capillaries to leak fluid into the space around the lungs (pleural effusion) or into the abdominal cavity (ascites).
The loss of blood and fluid during the second phase, if untreated, can worsen and can be fatal. In order to avoid that complication (sometimes called Dengue Shock Syndrome), a healthcare practitioner may hospitalize a patient with severe dengue fever so that falling blood pressure and dehydration caused by the loss of blood and fluids can be managed while the disease runs its course – generally a period of one to two weeks. During the following week of recovery, a person may develop a second rash that lasts a week or more.
Dengue fever is usually diagnosed via some combination of blood tests because the body’s immune response to the virus is dynamic and complex. Laboratory tests may include:
- Molecular tests for dengue virus (PCR)—detect the presence of the virus itself; these tests can diagnose dengue fever up to 7 days after the onset of symptoms and can be used to determine which of the 4 different serotypes of dengue virus is causing the infection.
- Antibody tests, IgM and IgG—detect antibodies produced by the immune system when a person has been exposed to the virus; these tests are most effective when performed at least 4 days after exposure.
- Complete blood count (CBC)—to look for low platelet count typical of the later stages of the illness and to detect the decrease in hemoglobin, hematocrit, and red blood cell (RBC) count (evidence of anemia) that would occur with blood loss associated with severe dengue fever
- Basic metabolic panel (BMP) – to monitor kidney function and look for evidence of dehydration that can occur with severe illness
How is the sample collected for testing?
A blood sample is collected by inserting a needle into a vein in the arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
Dengue fever testing is used to determine whether a person with signs and symptoms and recent potential exposure have been infected with the dengue virus. The infection is difficult to diagnose without laboratory tests because symptoms may initially resemble those of other diseases, such as chikungunya infection. Two primary types of testing are available:
- Molecular testing (polymerase chain reaction, PCR)—this type of test detects the genetic material of the dengue virus in blood within the first week after symptoms appear (fever) and can be used to determine which of the 4 serotypes is causing the infection. One type of Real-Time RT-PCR test can detect dengue and the two other mosquito-borne viruses, Zika, and chikungunya, and distinguish between the three. Only certain public health laboratories are able to provide the test after verifying that they can successfully perform the assay. Though the test is not available in hospitals or clinics, healthcare practitioners are able to order it through their state and local public health departments. Results can take from four days to two weeks, according to the Centers for Disease Control and Prevention (CDC). Molecular tests of blood are not likely to detect the virus after 7 days of illness. If the result of a PCR test is negative, an antibody test can be used to help establish a diagnosis, according to the CDC (see below).
- Antibody tests—these tests are primarily used to help diagnose a current or recent infection. They detect two different classes of antibodies produced by the body in response to a dengue fever infection, IgG and IgM. Diagnosis may require a combination of these tests because the body’s immune system produces varying levels of antibodies over the course of the illness. IgM antibodies are produced first and tests for these are most effective when performed at least 7-10 days after exposure. Levels in the blood rise for a few weeks, then gradually decrease. After a few months, IgM antibodies fall below detectable levels. IgG antibodies are produced more slowly in response to an infection. Typically, the level rises with an acute infection, stabilizes, and then persists long-term. Individuals who have been exposed to the virus prior to the current infection maintain a level of IgG antibodies in the blood that can affect the interpretation of diagnostic results.
What is NS1 Detection test?
- NS1 tests detect the non-structural protein NS1 of the dengue virus. This protein is secreted into the blood during dengue infection.
- NS1 tests have been developed for use in serum. Most of these tests use synthetically labeled antibodies to detect dengue NS1 protein.
How should it be used and at what time during infection?
- NS1 is detectable during the acute phase of dengue virus infections. NS1 tests can be as sensitive as molecular tests during the first 0-7 days of symptoms. After day 7, NS1 tests are not recommended.
- A positive NS1 test result is indicative of a dengue infection but does not provide serotype information. Knowing the serotype of the infecting virus is not necessary for patient care; however, if serotype information is needed for surveillance purposes, the sample should be tested by NAT.
- Though studies show that NS1 can be found in whole blood or plasma, most NS1 tests have been developed and evaluated in serum samples. While combined testing with an NS1 and IgM antibody test can usually provide a diagnostic result during the first 1-7 days of illness, a second, convalescent-phase specimen should be obtained and tested for IgM when both antigen and antibody tests are negative.
Interpretation of results
A positive NS1 test result confirms dengue virus infection without providing serotype information.
A negative NS1 test result does not rule out infection. People with negative NS1 results should be tested for the presence of dengue IgM antibodies to determine possible recent dengue exposure.