A 38-year-old male presents with high fever, severe retro-orbital pain, myalgia, and a maculopapular rash on day 5. Platelet count is 60,000/μL, NS1 antigen is positive. The most sensitive test to confirm dengue infection in the first 5 days of illness is:
- A NS1 antigen ELISA ✓
- B IgM ELISA (MAC-ELISA)
- C IgG ELISA
- D Hemagglutination inhibition test
Correct answer: A. NS1 antigen ELISA
Explanation
NS1 antigen is detectable from day 1 through day 5–9 of illness, making it the most sensitive serological marker in the acute (febrile) phase. IgM antibodies appear only from day 4–5 and peak at 2 weeks. IgG is used for secondary infection confirmation. The WHO dengue diagnostic algorithm recommends NS1 Ag ELISA or rapid test in the first five days.
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.