Quick Review Cards for Medical Laboratory Science

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.