Dengue Fever is caused by infection of RNA Flavivirus transmitted by a mosquito vector. Positive result in this test means that a person has been infected with Dengue virus within the recent weeks. But, positive result in IgG test and negative or low result in IgM test means it is likely that the person has had an infection sometime in the past. NS1 antigen is a non-structural protein found in infected patients from first day of fever upto to 5th day after the fever has begun. This test is meant for the detection of Dengue virus NS1 antigen so that it helps in the diagnosis of Acute Dengue infection.