A patient from a dengue-endemic district has fever, rash, and arthralgia. Dengue IgM ELISA is positive, but the clinician wants to distinguish current dengue infection from prior infection with another flavivirus, since IgM tests cross-react across this group. The most specific method to resolve this is:

• A Repeat IgM ELISA on a convalescent sample with a different commercial kit
• B Plaque reduction neutralisation test using type-specific virus strains ✓
• C NS1 antigen ELISA performed on the same serum
• D Peripheral blood smear examination for atypical lymphocytes

Explanation

The plaque reduction neutralisation test measures functional neutralising antibody against specific virus strains and is regarded as the most specific serologic method for distinguishing flavivirus infections, including dengue serotype determination. IgM ELISAs for flaviviruses show substantial cross-reactivity, so repeating them with another kit adds nothing. NS1 helps diagnose acute dengue but does not resolve past flavivirus exposure.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.