A new automated fourth-generation HIV screening assay with sensitive antigen detection module and high specificity.

New screening enzyme immunoassays, which permit the simultaneous detection of HIV antigens reduce the diagnostic window period between the time of immunodeficiency virus (HIV) infection and seroconversion. The VIDAS HIV DUO Ultra is an enzyme-linked fluorescent assay (ELFA) for the screening of HIV infection. It is performed with the fully automated VIDAS or mini-VIDAS instruments, which are so-called walk away systems. The detection limit is 3 pg of HIV-1 p24 Ag/mL serum. HIV antibody is detected with the same sensitivity as stand-alone third-generation antibody tests. The total incubation time is about 2 h. Results are calculated, interpreted, and printed by the VIDAS instrument. Usually, fourth-generation assays demand a special algorithm for the analysis of reactive samples. For the anti-HIV part of the assay, confirmation of reactivity should be done with an assay that lacks the p24-antigen detection module and when reactivity persists subsequently by immunoblot. For the p24-antigen part, confirmation of reactivity should be analyzed in an assay that lacks the anti-HIV detection part.