A patient positive for HIV on ELISA undergoes Western blot. Bands are present at gp120 and p24 only. According to WHO criteria, the Western blot result is:
- A Positive: any two bands confirms HIV
- B Negative: p24 alone is not significant
- C Indeterminate: WHO requires at least 2 envelope (gp) bands (e.g., gp41/gp120/gp160) for positivity ✓
- D Positive: gp120 alone confirms HIV infection
Correct answer: C. Indeterminate: WHO requires at least 2 envelope (gp) bands (e.g., gp41/gp120/gp160) for positivity
Explanation
WHO criteria for a positive HIV Western blot require at least 2 envelope glycoprotein bands (from: gp160, gp120, gp41); US CDC (earlier) required p24 + one envelope band; current WHO/NACO criteria favour ≥2 env bands. gp120 alone or gp120 + p24 without gp41 meets an indeterminate interpretation in strict WHO criteria, requiring repeat testing or alternative confirmatory assay. An indeterminate result needs clinical follow-up with repeat testing or 4th-generation antigen/antibody testing.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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