A patient presents with high-grade fever, intense headache, retroorbital pain, myalgia, and a characteristic skin rash appearing on day 3-4. Tourniquet test is positive. Which serological test confirms the diagnosis of dengue during the acute febrile phase (days 1-5)?
- A IgG antibody by ELISA
- B Widal test
- C NS1 antigen test ✓
- D Platelia dengue IgM capture assay
Correct answer: C. NS1 antigen test
Explanation
NS1 (non-structural protein 1) antigen is detectable from day 1 to day 5 of acute dengue fever — before antibody responses develop — making it the test of choice in the early febrile phase. IgM antibodies become detectable only after day 5 (secondary response in day 1-2). NS1 ELISA or rapid antigen tests have high sensitivity in early dengue. Widal test is for typhoid fever.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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