Dengue NS1 antigen test is a diagnostic test used for the early detection of dengue virus infection. Dengue NS1 is a glycoprotein secreted by dengue virus-infected cells during the acute phase of the disease. The test detects the presence of NS1 antigen in the blood sample of the infected person. The test is usually performed during the first 1-7 days of illness when the virus is actively replicating. Dengue NS1 antigen test is a rapid and reliable method for the early diagnosis of dengue infection, especially in areas where dengue is endemic. The test is often performed in conjunction with dengue IgM/IgG antibody tests to confirm the diagnosis of dengue virus infection.