Clinical application evaluation of two fourth-generation human immunodeficiency virus (HIV) screening assays in West China Hospital.

BACKGROUND: Fourth-generation human immunodeficiency virus (HIV) screening assays have been used in many laboratories. The Elecsys® HIV combi PT assay is a new kind of fourth-generation HIV screening assay developed to allow earlier detection of seroconversion. METHODS: A total of 271,845 routine specimens were detected using the Elecsys® HIV combi assay and Elecsys® HIV combi PT assay from September 2010 to December 2012 in a large university hospital. Repeatedly, reactive screening samples were confirmed according to recommended confirmatory algorithms. RESULTS: The false-positive rate and positive predictive value (PPV) of two assays are 0.08 and 78.35%, respectively, for the Elecsys® HIV combi assay and 0.07 and 82.21% for the Elecsys® HIV combi PT assay. Ninety-four percent cases with cutoff index ratio <15.0 were false-positive. When we set the specificity as 95.0 and 99.0%, PPV could increase to 98.7, 99.6, 98.8, and 99.7%, and sensitivity reduced to 99.2, 98.4, 98.5, and 96.8% for the Elecsys® HIV combi assay and the Elecsys® HIV combi PT assay, respectively. CONCLUSIONS: The Elecsys® HIV combi PT assay shows a better performance in specificity than the Elecsys® HIV combi assay. Most weakly reactive results were false-positive, this means it still need to be improved and it will need laboratory personnel to communicate with the clinical doctor and patients more properly about the result of the assay.

Performance evaluation of a new fourth-generation HIV Ag/Ab combination electrochemiluminescence immunoassay - evaluation of a new HIV assay.

A new fourth-generation HIV Ag/Ab electrochemiluminescence immunoassay for screening of HIV infection, the Elecsys HIV Combi PT (Roche Diagnostics, Penzberg, Germany) assay, is going to be commercially available in clinical laboratories in China. This assay was evaluated and compared with two commonly used assays: Elecsys HIV Combi assay and the Livzon anti-HIV-1/2 ELISA. Commercially available panels and 30 established HIV infection samples were tested to evaluate the sensitivity. In addition, a total of 675 routine clinical samples were collected and tested in West China Hospital to compare the specificity. Any reactive result from a screening test was retested and all reactive retested samples were confirmed with Western blot assay, Elecsys HIV Ag test, Elecsys HIV Ag confirmatory test or HIV-1 RNA NAT testing. According to the results of the HIV seroconversion panels, the Elecsys HIV Combi PT could detect seroconversion at the same bleed or at least one bleed earlier compared to the other two assays. Among the 675 clinical samples, most results were consistent except for one specimen with a false-negative result using Elecsys HIV Combi assay. In conclusion, the Elecsys HIV Combi PT has shown satisfactory sensitivity and specificity to be a screening test for HIV infection.

Comparative performance of electrochemiluminescence immunoassay and EIA for HIV screening in a multiethnic region of China.

BACKGROUND: The recent approval of 4th generation HIV tests has forced many laboratories to decide whether to shift from 3rd to these tests. There are limited published studies on the comparative evaluation of these two different assays. We compare the performance of fourth-generation electrochemiluminescence immunoassay (ChIA) and third-generation enzyme linked immunosorbent assay (EIA) for human immunodeficiency virus (HIV) screening and gauge whether the shift from EIA to ChIA could be better in a multiethnic region of China. METHODOLOGY/PRINCIPAL FINDINGS: We identified a large number of routine specimens (345,492) using two different assays from Jan 2008 to Aug 2011 in a teaching hospital with high sample throughput. Of the 344,596 specimens with interpretable HIV test results, 526(0.23%) of 228,761 using EIA and 303(0.26%) of 115,835 using ChIA were HIV-1 positive. The false-positive rate of EIA was lower than that of ChIA [0.03% vs. 0.08%, odds ratio 0.33 (95% confidence interval 0.24, 0.45)]. The positive predictive value (PPV) of EIA (89.6%) was significantly higher than that of ChIA (76.1%) (<0.001), reflecting the difference between the two assays. The clinical sensitivities of two assays in this study were 99.64% for EIA and 99.88% for ChIA. CONCLUSION: Caution is needed before shifting from 3rd to 4th generation HIV tests. Since none of these tests are perfect, different geographic and ethnic area probably require different considerations with regard to HIV testing methods, taking into account the local conditions.