HIV Confirmatory/Supplemental Tests Immunology Review 409
TEST
Western blot (WB)
Indirect immunofluorescent
assays (IFA)
NAAT
DETECTS
Ab to HIV
Ab to HIV
HIV RNA
COMMENTS
Traditional confirmatory test but not as sensitive as 4th-gen EIA or NAAT. Inter-
pretation is controversial but most labs report pos if at least 2 of the following
3 bands are present: p24, gp41, gp120/160. NAAT required following neg or
indeterminate results. Time-consuming, difficult to interpret.
Sensitivity & specificity comparable to Western blot. Not frequently used.
Expensive, subjective.
Qualitative test used for confirmation.
More specific than screening tests. Fewer false pos.