NS1 antigen test (nonstructural protein 1), is a test for dengue, introduced in 2006. It

allows rapid detection on the first day of fever, before antibodies appear some 5 or more days

later.

• A positive NS1 test result confirms dengue virus infection without providing serotype  information.
• A negative NS1 test result does not rule out infection. People with negative NS1 results should be tested for the presence of dengue IgM antibodies to determine possible recent dengue exposure.