From the Guidelines
A positive IgG test for dengue indicates that a person has been infected with the dengue virus at some point in the past, as IgG antibodies typically develop within 7-10 days after the onset of symptoms and can remain in the bloodstream for months or even years after recovery 1. This positive result represents a previous infection rather than an acute or current infection. For diagnosing a current dengue infection, IgM antibodies or viral detection methods like PCR would be more relevant, as IgG alone cannot distinguish between recent and past infections. In endemic areas, many people may have positive dengue IgG tests due to previous exposure to the virus. This past immunity can be clinically significant because secondary dengue infections sometimes carry a higher risk of severe disease due to antibody-dependent enhancement, where pre-existing antibodies may actually facilitate viral entry into cells during a subsequent infection with a different dengue serotype 1.
Some key points to consider when interpreting the results of dengue IgG testing include:
- The timing of infection cannot be determined based on IgG testing alone 1
- IgG antibodies can remain in the bloodstream for months or even years after recovery 1
- Secondary dengue infections may carry a higher risk of severe disease due to antibody-dependent enhancement 1
- In endemic areas, many people may have positive dengue IgG tests due to previous exposure to the virus 1
It is also important to note that the interpretation of dengue IgG test results should be considered in the context of the patient's clinical presentation, epidemiologic history, and other diagnostic test results 1.
From the Research
Positive IgG for Dengue
- A positive IgG test for dengue indicates that the individual has been infected with the dengue virus at some point in the past 2, 3, 4.
- The presence of IgG antibodies suggests a secondary infection, which can increase the risk of severe forms of the disease 3, 4, 5.
- IgG antibodies can be detected in the blood several days after the onset of symptoms and can remain present for months or even years after recovery 4, 5.
- The IgG to IgM ratio can be used to discriminate between primary and secondary dengue infections, with a ratio of ≥ 1.14 indicating secondary infection 5.
Interpretation of Test Results
- A positive IgG test result with a negative IgM test result indicates a past infection or immunity to the dengue virus 3, 4.
- A positive IgG test result with a positive IgM test result indicates a recent secondary infection 3, 4, 5.
- The sensitivity and specificity of IgG tests can vary depending on the test used and the population being tested 2, 4.