Journal of Virological Methods 137 (2006) 292–297 Evaluation of a new fourth generation enzyme-linked immunosorbent assay, the LG HIV Ag–Ab Plus, with a combined HIV p24 antigen and anti-HIV-1/2/O screening test Joon-Sup Yeom a,1 , Gyo Jun b,1 , Young Chang c , Mi-Jin Sohn d , Seungbum Yoo d , Eunkyung Kim d , Seung-Ho Ryu e , Hee-Jung Kang f , Young-A Kim c , Sun-Young Ahn c , Je-Eun Cha c , Sung-Tae Youn g , Jae-Won Park c,∗ a Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea b Department of Biochemistry, Gachon Medical School, Incheon, Republic of Korea c Department of Microbiology, Gachon Medical School, 1198 Kuwol-dong, Namdong-gu, Incheon 405-760, Republic of Korea d Biotech Research Institute, LG Life Sciences, Daejeon, Republic of Korea e Department of Occupational Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea f Department of Laboratory Medicine, Hallym University College of Medicine, Kyeonggi-do, Republic of Korea g Graduate School, Gachon Medical School, Incheon, Republic of Korea Received 26 December 2005; received in revised form 1 July 2006; accepted 4 July 2006 Available online 14 August 2006 Abstract The LG HIV Ag–Ab Plus, a new fourth generation diagnostic assay for HIV infection, was evaluated in comparison to the Enzygnost HIV Integral, an established fourth generation HIV assay. The LG assay showed 100% sensitivity with 109 samples with anti-HIV-1, anti-HIV-2 or anti-HIV-1 group O reactivity. It also detected correctly all 51 positives on three BBI performance panels, slightly outperforming the Enzygnost HIV Integral, which detected 50. The specificity of the LG HIV Ag–Ab Plus was 99.9% with 999 sera from healthy blood donors, which was slightly inferior to the performance of the Enzygnost HIV Integral, which had 100% specificity. The LG assay showed 100% specificity with 81 specimens with underlying diseases including hepatitis B, demonstrating a low risk of cross-reactivity with other infections. The reduction of the diagnostic window by the LG HIV Ag–Ab Plus, compared to a third generation HIV assay, was 6.3 days. The LG assay also showed sufficiently high intra-person and inter-person reproducibility. The overall performance of this new fourth generation HIV assay was adequate for screening and diagnosis of HIV infection. © 2006 Elsevier B.V. All rights reserved. Keywords: HIV serodiagnosis; ELISA; Sensitivity; Specificity; Seroconversion 1. Introduction A number of commercial enzyme-linked immunosorbent assays (ELISAs) for screening or diagnosis of HIV infection have been developed since 1985. First generation ELISAs that employed viral lysate antigens for detection of anti-HIV human IgG had nonspecific reactions between antibodies and cell anti- gens. Second generation ELISAs provided improved sensitiv- ∗ Corresponding author. Tel.: +82 32 460 2184; fax: +82 32 421 5537. E-mail address: seorak@dreamwiz.com (J.-W. Park). 1 These authors contributed equally to this work. ities and specificities by employing recombinant or synthetic peptide antigens (Thorstensson et al., 1998; Brust et al., 2000). These new assays, however, could not reduce significantly the rate of false positive results because they were based on the same principle as the first generation assays. To overcome the limita- tions of the early generation assays, third generation assays were developed based on the new assay principle of a double-antigen sandwich. Later, several laboratories reported that many of the established HIV assays failed to detect some of the HIV sub- types, particularly HIV-1 group O (Loussert-Ajaka et al., 1994; Apetrei et al., 1996; Christiansen et al., 1996; Thorstensson et al., 1998). Thus, the third generation assays were improved further with modifications that allowed detection of highly divergent 0166-0934/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jviromet.2006.07.002