QUANTITATIVE DETECTION OF HUMAN-IMMUNODEFICIENCY-VIRUS (HIV) ANTIGEN BY THE ENZYMUN-TEST - COMPARISON WITH ALTERNATIVE ASSAYS AND NUCLEIC-ACID SEQUENCE-BASED AMPLIFICATION OF HIV TYPE-1 RNA

A new modular automated enzyme immunoassay (EIA) (Enzymun-Test HIV Ag; Boehringer Mannheim) for quantitative human immunodeficiency virus (H IV) antigen detection was evaluated by testing a panel of 1,506 serum samples, including seroconversions, dilution series, follow up samples from patients under antiretroviral therapy, single serum specimens fr om HN-seropositive individuals in different stages of infection, poten tially cross-reactive samples, and sera from HIV-negative hospitalized patients. The Abbott HIV type 1 (HIV-1) antigen monoclonal antibody a ssay served as the reference assay, and nucleic acid sequence-based am plification (Organon Teknika) for quantitative amplification of HIV-1 RNA was used for follow-up of patients under antiretroviral chemothera py. The Boehringer Mannheim and Abbott EIAs showed concordant results for the early detection of HIV antigen in all the seroconversion panel s. The follow-up samples from 29 HIV-infected individuals under antire troviral therapy gave divergent results between both antigen tests. Fo r the detection of HIV antigen in single serum samples from HIV-infect ed patients in different stages of HIV infection, a higher number of p ositive samples was detected with the Abbott HIV-1 antigen monoclonal antibody assay in samples from patients in stages II and III of HIV in fection. The Enzymun-Test detected three more positive samples than di d the Abbott assay among the samples of patients with AIDS. The concor dance on a sample-to-sample basis between the Boehringer Mannheim and Abbott EIAs was 98.6%. The sensitivity of the Enzymun-Test in comparis on to the reference assay was 97.2%; the specificity was 98.8%. Althou gh no close correlation could be found between the amount of viral RNA in serum detected by nucleic acid sequence-based amplification and th e concentration of HIV antigen, a high HIV-1 RNA copy number was mostl y associated with high levels of HIV antigen. In conclusion, the Enzym un-Test permits accurate HIV antigen detection and offers, in contrast to previous assays, the possibility of completely automated detection .