Performance evaluation of the new Access HIV Ag/Ab combo assay on the DxI 9000 Access Immunoassay Analyzer

Fourth-generation HIV immunoassays have been developed to reduce the window period of detection during seroconversion period, allowing for the detection of early and established infections. The aim of this work was to evaluate a newly developed assay, Access HIV Ag/Ab combo on the novel high throughput DxI 9000 Access Immunoassay Analyzer (Beckman Coulter, Inc.). The assay allows for simultaneous qualitative detection and differentiation of HIV-1 p24 antigen and HIV-1/2 antibodies.

Assay performance was compared to two gold standard assays, the Abbott Architect HIV Ag/Ab Combo and Roche Elecsys HIV Duo, and assessed in a multicenter study, using a wide panel of samples (n > 9000, clinical samples and viral lysates) representative of genetic diversity for both antibodies and antigens, early phases of infection, negative, and cross-reacting samples.

The clinical sensitivity was 100 % for clinical samples as well as for viral lysates. Data on viral lysates and early detection on seroconversion panels showed a better result with the Access assay. Analytical sensitivity showed a limit of p24 detection determined around 0.2 IU/mL. The overall specificity was 99.91 %, and no interference was found using the potentially cross-reactive samples.

In conclusion, the Access HIV Ag/Ab combo assay demonstrated its ability for accurate diagnosis of chronic as well as primary HIV infections on the DxI 9000 Analyzer, despite the high level of genetic diversity of these viruses.