Evaluation of Three Second‐Generation and Three Confirmatory Assays for Antibodies to Human Immunodeficiency Virus

Abstract

The second-generation enzyme immunoassays (EIAs) for antibodies against human immunodeficiency virus (HIV) from three manufacturers (Abbott, Organon, Wellcome) and three anti-HIV confirmatory tests, i.e. Western Blot (WB, Biotech, Dupont), radioimmunoprecipitation assay (RIPA, CLB) and a competitive immunoassay (CIA, Abbott) were evaluated on a panel of 6,488 serum samples, which had previously been used for the comparison of seven first-generation EIAs. For the present study the panel was expanded with sequential serum samples from 12 individuals followed at 1- to 3-month intervals during seroconversion for anti-HIV. The second-generation EIAs and confirmatory tests were significantly more sensitive than the first-generation EIAs as was demonstrated by detection of 10- to 100-fold higher endpoint titers in anti-HIV-positive sera as well as by earlier detection of anti-HIV in 7-11 of the 12 subjects, who seroconverted. In all sera obtained during early HIV infection anti-gp 160/120env antibodies (WB, CIA) were found in addition to anti-p24 (WB, RIPA) and in serial two-fold dilutions of these ''seroconversion samples'' the new Abbott EIA and RIPA were significantly more sensitive than WB (p < 0.05), whereas CIA and the new Organon EIA were significantly less sensitive than WB (p < 0.05). The new Wellcome EIA was not statistically less sensitive than WB. The CIA was as sensitive as WB for antibodies to envelope proteins (gp41, gp 160, gp120,), but considerably less sensitive for core (p24) antibodies, as was shown in sera obtained during early as well as later clinical stages of HIV infection. The frequencies of false-positive reactions by the second-generation EIAs on a panel of 292 tricky samples from patients with e.g. autoimmune diseases and acute viral infections and in a panel of 283 selected donor sera, with false-positive reactivities in the first-generation EIAs were: Abbott 1.0%, 0.3%, Wellcome 0%, 0%, and Organon 0.3%, 0%. By the confirmatory tests they were: WB (anti-p24) 1.7%, 10.2%; RIPA (anti-p24) 0.3%, 1.1%; and CIA 0.3%, 0.3%. It is concluded that application of highly sensitive second-generation EIAs in blood banks is important to further reduce the risk of posttransfusion HIV infection.