Presumptive diagnosis made with HIV-1/2 Ag/Ab immunoassays. - These immunoassays detect viral p24 Ag capsid protein and IgG Abs to HIV-1/2. Very high sensitivity/specificity.- ⊕ tests are confirmed with HIV-1/2 Ab-differentiation immunoassays which determine whether patient has HIV-1 or HIV-2.

If inconclusive differentiation assay, an HIV-1 nucleic acid amplification test (NAAT) is performed.- if NAAT Θ, patient had false positive initial Ag/Ab immunoasay.

- Viral load tests determine the amount of viral RNA in the plasma. High viral load associated with poor prognosis. Also use viral load to monitor effect of drug therapy.- Use HIV genotyping used to determine appropriate therapy.

AIDS diagnosis ≤200 CD4⁺ cells/mm³ (normal 500-1500 cells/mm³).HIV ⊕ with AIDS defining condition or CD4⁺ percentage <14%.