Dengue Testing Breakdown: Understanding ELISA’s Role in Detecting Dengue Virus

Dengue Testing Breakdown: Understanding ELISA’s Role in Detecting Dengue Virus


Dengue Testing Breakdown

Dengue fever, a viral infection spread by the bite of Aedes mosquitoes, is an annual epidemic in many tropical and subtropical regions worldwide. Its symptoms vary from mild fever to severe, potentially life-threatening complications.

The infection is becoming steadily more dangerous with environmental changes and poses a major public health threat globally. For instance, recent data show that 101,192 people were infected with dengue in India in 2018, while 110,473 were infected in 2022.

These growing numbers underscore the importance of timely testing for dengue and proper medical care. While there are various dengue testing methods available, one of the most widely used tests is the enzyme-linked immunosorbent assay (ELISA), which we will discuss in this article.

Understanding ELISA (Enzyme-Linked Immunosorbent Assay)

The ELISA is a common test to find antigens or antibodies in the blood. Antibodies are proteins made by your body’s immune system in response to harmful substances called antigens. The ELISA test requires a small blood sample, which is typically collected from a vein in your arm.

This sample is then sent to the laboratory, where it’s mixed with specific enzymes that are designed to react with the targeted antibody or antigen. If the target antigen/antibody is present in the sample, the test solution will change color.

There are a few types of ELISA tests used to detect dengue:

IgM-capture ELISA: This test specifically detects IgM antibodies, which are produced by the body early in the infection. IgM-capture ELISA is useful for diagnosing acute or recent dengue infections. The dengue MAC-ELISA is an IgM capture ELISA test to find out if someone has the dengue virus infection.

IgG-capture ELISA: This test detects IgG antibodies, which are produced later in the infection and can remain in the body for a longer period. IgG-capture ELISA helps identify past dengue infections or determine if a person has developed immunity against the virus.

NS1 antigen test: The NS1 test detects a specific non-structural protein called NS1 that the dengue virus produces. The test works by using special antibodies that are designed to recognize and attach to the NS1 protein of the dengue virus.

Thus, these ELISA tests can detect dengue at different stages and help in diagnosing and monitoring this infection.

When Is the Right Time for Testing?

When a person gets dengue for the first time, their body slowly starts making IgM antibodies, which can be detected in the blood around 3 to 5 days after they start feeling sick. By day 10, almost everyone will have these antibodies. IgM levels reach their highest point about two weeks after symptoms start, then decrease gradually to undetectable levels after a few months.

On the other hand, IgG antibodies start showing up in the blood about a week after symptoms begin, but they keep increasing for a while and can stay in the body for a long time, even for life.

So, to detect dengue, IgM tests should be done around 3 to 5 days after symptoms start, and IgG tests can be done around a week later.

NS1 protein is also found in the blood during the early stage of dengue infection. Tests that look for NS1 can be just as good at finding the virus within the first week of symptoms.

Interpreting ELISA Results for Dengue Virus

Now that you understand how ELISA works, let’s talk about how the results are analyzed. Interpreting ELISA results for dengue virus can be a bit complex and is best done by a professional. But here’s a general idea of what your results could mean:

  • Negative IgM: If IgM is negative before the 8th day of illness and the results of other tests such as NS1 are also negative or absent, it’s uncertain whether it’s dengue. Another sample should be taken after the 7th day for later testing.
  • If IgM is negative after 7 days of symptoms, along with negative NS1 results, it’s unlikely to be a recent dengue infection.
  • If IgM changes from negative to positive in paired samples (first collected within 7 days of illness, second after symptoms improve), it suggests a current dengue infection.
  • Positive IgM: If the IgM test is positive, it suggests that the person has likely had a recent dengue virus infection.
  • Positive IgG: If the result is positive for IgG antibodies but IgM antibodies or NS1 antigen are absent, it could mean you are currently infected with the virus or have been exposed to it in the past.
  • Positive NS1: If the result is positive for NS1, it suggests that the person likely has a dengue infection, but it doesn’t tell us which specific type of dengue virus has caused it.
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It is important to note that due to possible cross-reactions with other viruses and nonspecific reactions, ELISA results can be tricky to understand.

Hence, the dengue MAC-ELISA is usually combined with molecular tests, such as the nucleic acid amplification tests (NAATs), to obtain a diagnostic result in the first week of infection.

NAATs like the reverse transcription-polymerase chain reaction (rtPCR) test can detect dengue virus RNA (the genetic material of the virus) in the blood samples early in the infection. Unclear IgM results may also be confirmed through other specific tests like plaque reduction neutralization testing (PRNT).

Advantages and Limitations of ELISA in Dengue Testing

Like any detective tool, ELISA has its strengths and weaknesses. On the positive side, ELISA is a highly sensitive and specific method, meaning it can accurately detect even tiny amounts of the dengue virus antigen or its antibodies in a sample. It’s also relatively easy to perform and can handle large numbers of samples simultaneously.

However, ELISA also has its limitations. It can sometimes produce false-positive or false-negative results, which can lead to misdiagnosis or delayed treatment. Factors like the timing of the test, cross-reactivity with other viruses, and improper sample handling can all contribute to inaccurate results.

To overcome these challenges, researchers and healthcare professionals are continuously working on improving ELISA techniques and developing strategies to enhance their accuracy and efficiency in dengue detection.

Conclusion

ELISA plays a vital role in detecting dengue virus infections, offering a reliable method for diagnosis. While understanding the results can be challenging, it is important to remember that getting tested for dengue is beneficial.

In instances where the initial ELISA test results are not definitive, additional tests can be performed to confirm the diagnosis accurately. The key takeaway is that getting tested for dengue using ELISA is an essential step in identifying the infection and receiving prompt and proper medical care.

If there are any concerns or uncertainties regarding the test results, healthcare professionals will guide you through the tests required for correct diagnosis and treatment.

About The Author:

Laxman is a Lifestyle Blogger who is a fitness enthusiast and also a digital marketer.



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