Dengue Ns1 Antigen Rapid Test

Dengue antigen test detects the non-structural protein NS1 of the dengue virus. This protein is secreted by the virus in the blood during dengue infection. NS1 tests have been designed for use in blood serum. Most of these tests use laboratory-labelled antibodies to detect the dengue NS1 protein.

NS1 antigen is detectable only during the acute phase of dengue infections. NS1 tests are as sensitive as molecular tests between 0-7 days of symptoms. After day 7, NS1 tests are not usually prescribed.

A positive Dengue NS1 Antigen test is diagnostic of a dengue infection but does not give serotype information. Knowing the serotype of a particular virus is not necessary for patient care; however, if serotype information is needed for surveillance purposes, the blood sample should be tested by NAT.

Studies show that NS1 can be found in whole blood or plasma, but NS1 tests have been developed and evaluated in serum samples. This test helps detect the dengue infection early and thus the treatment can be started faster.

You can get a false negative on the Dengue NS1 Antigen test if done before 24-48 hours or after 9-10 days. The antigen is rarely found in infected blood after 9-10 days from the onset of infection.

First used in 2006, it was adopted in India in 2010 to control the dengue epidemic. The test can also detect flavivirus and other viruses which go undetected in the body.

The Dengue NS1 Ag Strip test detects the NS1 antigen formed immediately after a dengue infection. The test kit should be ideally checked after 15 minutes of the blood being drawn. Then repeated observations should be made at 30 minutes for confirmation. If the test comes positive, dengue infection is present in the body in its early stages. Antibodies IgM and IgG levels are usually low in the onset stage. Hence, the antibody-based IgM-Elisa test is done again after 5 days.

NS1 was detectable from day 1 to day 12 of fever. The positive detection rate of NS1 antigen ELISA, RT-PCR and IgM ELISA.

The following table shows the presence of colour bands and what these values mean in the NS1-rapid antigen test.

The Dengue NS1 Antigen test is given as the value of antigen test detected and not detected.

Detected - antigen for dengue virus is seen in the blood. The initial phase of infection can be treated at an early stage. You may then start treatment and do an antibody test 1-2weeks after the start of treatment. This is considered a positive report of Dengue NS1 Antigen.

Not detected- The antigen for the dengue virus was not present. This is considered a negative report of Dengue NS1 Antigen.

You can also get a false-negative result if done too early or too late (before 24-48 hrs of symptoms or 12 days after symptoms started).

Dengue fever - acute onset of symptoms