During a dengue outbreak, a patient in day 4 of illness has fever, thrombocytopenia (platelets 40,000/µL), and a tourniquet test positive. Which combination of diagnostic tests is most appropriate at this stage?
- A RT-PCR for dengue RNA only
- B IgM capture ELISA (MAC-ELISA) only
- C NS1 antigen ELISA and anti-dengue IgM/IgG ELISA ✓
- D Virus isolation in Aedes mosquito cell line (C6/36)
Correct answer: C. NS1 antigen ELISA and anti-dengue IgM/IgG ELISA
Explanation
On day 4 of dengue fever, NS1 antigen is still detectable (present from day 1–9 of illness, declining thereafter) while IgM antibodies are typically rising (detectable from day 5–6 in primary infection and day 3–4 in secondary). Combining NS1 antigen ELISA with anti-dengue IgM/IgG ELISA maximises sensitivity at this transitional time point. RT-PCR is most useful in the first 5 days (viraemic phase) and is expensive. MAC-ELISA for IgM alone may miss early cases. Virus isolation is a research tool, not routine diagnostics.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.