The dengue NS1 antigen test is most useful in which phase of dengue fever for early diagnosis?
- A Day 7–10 of illness
- B First 1–5 days of fever (febrile phase) ✓
- C After day 14 of illness
- D During defervescence only
Correct answer: B. First 1–5 days of fever (febrile phase)
Explanation
Dengue NS1 (Non-Structural Protein 1) antigen is detectable in serum from day 1 to day 5 of fever (febrile phase) before IgM antibodies appear, making it useful for early diagnosis. After day 5–7, NS1 levels decline while IgM antibodies become detectable. IgG is used for secondary dengue diagnosis. The NS1 ELISA has a sensitivity of 60–90% and near 100% specificity for dengue.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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