Use

Dengue NS1 antigen is present in serum during the acute phase of dengue virus infection, typically within days 1–9 after symptom onset. Detection of NS1 antigen allows accurate diagnosis in the early (febrile) phase, potentially before RNA or IgM detection assays become positive ([questdiagnostics.com](https://www.questdiagnostics.com/healthcare-professionals/clinical-education-center/faq/faq169?utm_source=openai)).