An HIV Diagnostic Testing Algorithm Using the cobas HIV-1/HIV-2 Qualitative Assay for HIV Type Differentiation and Confirmation.

HIV-1 and HIV-2 diagnostic testing algorithms recommended by the Centers for Disease Control involve up to three tests and rely mostly on detection of viral antigen and host antibody responses. HIV-1 p24 antigen/HIV-1/2 antibody reactive specimens are confirmed with an immunochromatographic HIV-1/HIV-2 antibody differentiation assay and negative or indeterminate results from the differentiation assay are resolved by an HIV-1-specific nucleic acid amplification test (NAT). The performance of a proposed alternative algorithm using the cobas HIV-1/HIV-2 Qualitative NAT as the differentiation assay was evaluated in subjects known to be infected with HIV-1 (N=876) or HIV-2 (N=139), at low (N=6017) or high (N=1020) risk of HIV-1 infection, or at high-risk for HIV-2 infection (N=498) (Study A). The performance of the cobas HIV-1/HIV-2 Qualitative test was also evaluated by comparison to an HIV-1 or HIV-2 alternative NAT (Study B). The HIV-1 and HIV-2 overall percent agreements (OPA) in Study A ranged from 95%-100% in all groups. The positive percent agreements (PPA) for HIV-1 and HIV-2 were 100% (876/876) and 99.4% (167/168) respectively for known positive groups. The negative percent agreement in the HIV low-risk group was 100% for both HIV-1 and HIV-2. In Study B, the HIV-1 and HIV-2 OPA ranged from 99%-100% in all groups evaluated (N: 183 to 1030), and the PPA for HIV-1 and HIV-2 were 100% and 99.5% respectively for known positive groups. The cobas HIV-1/HIV-2 Qualitative Assay can discriminate between HIV-1 and HIV-2 based on HIV RNA, and can be included in an alternative diagnostic algorithm for HIV.