A 30-year-old woman presents on day 3 of febrile illness with headache, myalgia, and retro-orbital pain in a dengue-endemic district. Platelet count is 95 × 10⁹/L. Which single test has the highest sensitivity for confirming dengue at this stage?
- A Dengue-specific IgM ELISA
- B Dengue-specific IgG ELISA
- C NS1 antigen detection ✓
- D Haemagglutination inhibition titre on paired sera
Correct answer: C. NS1 antigen detection
Explanation
NS1 antigen is detectable from day 1 through approximately day 5 to 7 of illness in both primary and secondary infections, making it the most sensitive single test in the first week. IgM antibodies usually become detectable around day 5 and peak in the second week, so they would be falsely negative on day 3. IgG rises late in primary infection and persists for life, so a single IgG cannot confirm acute dengue.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.