In the Western blot confirmatory test for HIV, a result is interpreted as 'indeterminate' when:
- A Bands are present for gp41 only
- B Bands present but criteria for positivity (2 of gp120/160, gp41, p24) are not met ✓
- C A single band is present at gp160 alone
- D No bands are visible
Correct answer: B. Bands present but criteria for positivity (2 of gp120/160, gp41, p24) are not met
Explanation
A Western blot is indeterminate when one or more bands are present but they do not fulfill the standard positive criteria — which require reactivity to at least two of the three major HIV antigens: gp120/160 (envelope), gp41 (transmembrane), and p24 (core). Indeterminate results occur during early seroconversion or in unrelated conditions causing cross-reactive bands. No bands indicates a negative result. An isolated gp41 band also falls under indeterminate, making option B the most complete and accurate description.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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