Dengue NS1 antigen test is MOST useful in which window of illness?
- A Days 1–5 of fever (acute febrile phase) ✓
- B After day 7 of illness
- C During defervescence (day 4–6)
- D In the recovery phase (day 8–14)
Correct answer: A. Days 1–5 of fever (acute febrile phase)
Explanation
Dengue NS1 antigen is detectable in blood from day 1 and peaks by day 3–5 of illness, making it most useful in the first 5 days of fever (acute febrile phase). IgM antibody appears from day 4–5 and is more useful after day 5. NS1 antigen is negative or very low by day 7 when antibody-based tests become reliable.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.