A patient has a positive ELISA for HIV but a negative Western blot with bands appearing at gp41 only. The MOST appropriate interpretation is:

• A False positive ELISA — patient is HIV negative
• B Indeterminate Western blot — repeat testing in 4-6 weeks with RNA PCR for confirmation ✓
• C HIV-2 infection — Western blot for HIV-2 should be performed
• D True positive — gp41 band alone is sufficient for Western blot confirmation

Explanation

WHO/CDC criteria for a positive HIV Western blot require at least two of three bands: p24 (core), gp41 (transmembrane), and gp120/gp160 (envelope) — or at least one band for gp41/gp160 plus p24 in some criteria; a single gp41 band is indeterminate (not negative, not positive), which can occur in early seroconversion, HIV-2 cross-reactivity, or non-specific reactions. The correct management is HIV RNA NAT (nucleic acid test) for confirmation and repeat serology in 4-6 weeks. A single band does NOT confirm HIV. HIV-2 would show cross-reactive bands but should be considered if indeterminate persists.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.