What is the Difference Between Dengue IgG IgM and NS1

The key difference between dengue IgG IgM and NS1 is that IgG is completely detectable from exposure to the dengue virus from the 3^rd week of exposure up to 24 weeks while IgM is detectable from the 7^th day of exposure up to 24 weeks and NS1 is detectable from the 1^st day up to the 7^th day of exposure.

Dengue virus is a single-stranded RNA virus of the family Flaviviridae that is mosquito-borne. Up to now, four serotypes of the dengue virus have been found. During the detection of the dengue virus, IgG, IgM, and NS1 play a major role. Dengue specific IgM and IgG are the most common diagnostic methods utilized.

CONTENTS

1. Overview and Key Difference
2. What is Dengue IgG  
3. What is Dengue IgM  
4. What is Dengue NS1
5. Similarities – Dengue IgG IgM and NS1
6. Dengue IgG vs IgM vs NS1 in Tabular Form
7. Summary – Dengue IgG vs IgM vs NS1

What is Dengue IgG?

IgG is immunoglobulin G found in blood and lymph that is produced and released by plasma B cells. IgG antibodies represent 75 % of serum antibodies in humans. The complete development of IgG antibodies occurs after three weeks following exposure in immunocompetent individuals. However, IgG is detectable from the 3^rd day of symptoms and may remain up to 6 months post-infection. The production of IgG antibodies related to the dengue virus is consistent with acute phase infection.

In the absence of infection, IgM antibodies are not detected. However, this could be a false negative due to the collection of the sample prior to the production of IgG antibodies by the body against the dengue virus. Hence, a second sample should be analyzed after 10-12 days following exposure if the individual remains suspected of dengue virus. The test performed for the detection of IgG antibodies is IgG ELISA. Positive results indicate the presence of the dengue virus. False positives could also indicate the presence of other types of viruses such as Zika virus, West Nile virus, Flavivirus, etc. In such instances, it is vital to obtain a detailed history of the patient followed by further laboratory testing.

What is Dengue IgM?

IgM is immunoglobulin M found in blood and lymph fluid. It is the first antibody produced by the body during a new infection. IgM is one of the several types of antibodies produced by the body to induce immune reactions against infections. During dengue infection, dengue virus-specific IgM and other neutralizing antibodies are produced after the end of the first week of symptoms. They are not produced in the first seven days of symptoms. IgM is detectable after the 5^th day of exposure. IgM levels are usually variable. They are completely present on the 7th day of infection and may persist more than 12 weeks post-onset of symptoms.

During serotype determination, IgM antibodies are not vital. The dengue MAC-ELISA (IgM Antibody Capture Enzyme-Linked Immunosorbent Assay) is the test for the qualitative detection of the dengue virus. During the test, MAC ELISA captures human IgM antibodies using anti-human IgM antibodies with the addition of dengue virus antigens. Two specimen types are used for the dengue IgM test. They are serum and cerebrospinal fluid. Test results of MAC ELISA can be either negative or positive. Positive IgM test result classifies the patient as a presumptive or recently dengue infected individual. Negative IgM results are complicated and should be re-done with NAAT (nucleic acid amplification test) to confirm the presence or absence of dengue IgM antibodies. Dengue IgM detection kit is commercially available.

What is Dengue NS1?

Dengue NS1 is a protein secreted into the blood during dengue infection. This is a non-structural protein detected during the acute phase of dengue infection. The NS1 test detects the NS1 protein and is developed for use in blood serum. This test use antibodies synthetically labelled to detect the protein NS1. These tests have a high sensitivity rate during the first seven days of symptoms. NS1 tests are not recommended after the 7^th day of symptoms since the sensitivity of the test will be reduced and provide false results.

During results analysis, a positive NS1 test indicates the presence of dengue infection but not the serotype. Obtaining serotype information is not vital for patient care. However, it is important for surveillance purposes. Dengue NS1 protein is present in whole blood or plasma. As a clinical norm, dengue NS1 test is developed, performed, and evaluated in blood serum samples.

During the dengue NS1 test, the diagnostic result is obtained with the combination of dengue IgM antibody. This is for the first seven days of symptoms. If both antigen and antibody tests are negative, a second specimen from the recovering phase should be obtained and tested for IgM. Dengue NS1 test provides two types of results as negative and positive test results. During a positive test result, the test confirms the presence of dengue infection. During a negative test result, the test does not rule out the probability of dengue infection. Hence, the test is performed with the presence of dengue IgM antibodies. This will confirm if there is any dengue exposure in the patient. Dengue NS1 test kits are commercially available.

What are the Similarities Between Dengue IgG IgM and NS1?

• All three IgG, IgM and NS1 are diagnostic tools for the detection of the dengue virus.
• All three are present in the blood following exposure to the dengue virus.
• IgG IgM and NS1 test analysis use the serum as the specimen.
• There are commercial test kits for the detection of all three types.
• IgG, IgM and NS1 based dengue virus tests are significantly accurate than other tests to detect dengue virus.

What is the Difference Between Dengue IgG IgM and NS1?

The key difference between dengue IgG IgM and NS1 is their detectable periods upon infection. Dengue IgG is completely detectable after the 3^rd week of exposure while the dengue IgM is detectable during the 7^th day up to 24 weeks of post-exposure. Meanwhile, dengue NS1 detection is critical since it has to be done during the first 07 days of exposure. IgG and IgM are antibodies.

The below infographic presents the differences between dengue IgG IgM and NS1 in tabular form for side by side comparison.

Summary – Dengue IgG vs IgM vs NS1

Dengue virus is a mosquito borne, single-stranded RNA virus of the family Flaviviridae. Dengue IgG, IgM and NS1 play a major role in detecting dengue and are the most accurate test subjects. IgG is immunoglobulin G found in blood and lymph produced and released by plasma B cells. IgG is detectable from the 3^rd day of symptoms and may remain up to 6 months post infection. IgM is immunoglobulin M found in blood and lymph fluid, and it is the first antibody produced by the body during a new infection. They are detected on the 7th day of infection and may persist more than 12 weeks post symptom onset. Dengue NS1 is a protein secreted into the blood during dengue infection. NS1 tests are not recommended after the 7^th day of symptoms since the sensitivity of the test will be reduced and provide false results. This summarizes the difference between dengue IgG IgM and NS1 IgG IgM and NS1.

Reference:

1. “Dengue Virus Antigen Detection.” Centers for Disease Control and Prevention, 3 May 2019.
2. “Test ID: DENGM Dengue Virus Antibody, IGG and IGM, Serum.” Mayo Clinic Labs.

Image Courtesy:

1. “Dengue testing” By James Heilman, MD – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Course of Dengue illness”  By Dr Graham Beards – Own work (CC BY-SA 3.0) via Commons Wikimedia
3. “SAG Dengue-Virus 160413 01” By Girish Khera, Scientific Animations – (Public Domain) via Commons Wikimedia