Table 3.

Diagnostic Assays Used for HIV Testing

HIV antibody tests

EIAs, WB , IFAs

Rapid EIAs available; can be performed on blood or saliva specimen

Traditional HIV antibody testing has required positive EIA result, confirmed by positive WB (or IFA) result for HIV diagnosis

Combination HIV antigen and antibody (fourth-generation) tests

Detects anti-HIV IgM and IgG antibodies and p24 antigen

IgM and antigen detection components improve sensitivity for detecting primary HIV infection

Not appropriate for HIV diagnosis in infants (age <18 months)

Nucleic acid amplification tests

HIV DNA PCR; used only for infant diagnosis

HIV RNA PCR and other assays; quantitative and qualitative; used for infant diagnosis and primary HIV infection diagnosis (quantitative assays also used for monitoring virologic response to antiretroviral therapy)

EIA=enzyme immunoassay; HIV=human immunodeficiency virus; IFA=immunofluorescent assay; PCR=polymerase chain reaction; WB=Western blot.

See Centers for Disease Control and Prevention (26) for additional information.