Threshold value of LIAISON XL anti-HCV screening assay predicting positive immunoblotting results.

Some international guidelines recommend evaluating the need to confirm positive anti-hepatitis C virus (HCV) antibody screening results by means of a more specific antibody or molecular biology test on the basis of a screening threshold value (such as the sample signal/cut-off ratio) that can predict the positivity of additional antibody testing in at least 95% of cases. The aim of this study was to determine the threshold value of the DiaSorin LIAISON XL chemiluminescence test. Two hundred and twenty-eight routine laboratory samples that were chemiluminescence positive for anti-HCV antibodies but had different signal/cut-off ratios were assayed using immunoblotting, which indicated that 155 (68.0%) were positive, 40 (17.5%) were negative, and 33 (14.5%) were indeterminate. When the samples were divided on the basis of their signal/cut-off ratios, 95.5% of the samples with a ratio of ≥3.5 were positive as against 74.1% of the positive or indeterminate samples with a ratio of <3.5. Statistical analysis using Youden's index and a receiver operating characteristic curve showed that the optimum cut-off value was 3.65. These findings indicate that, when using the LIAISON XL system for anti-HCV antibody screening, a signal/cut-off ratio of ≥3.65 makes further confirmatory tests unnecessary.

Evaluation of LIAISON® XL system for HBsAg, and anti-HCV and anti-HIV/Ag p24.

The aim of this study was to compare the data obtained using the new LIAISON® XL chemiluminescence system to search for HBsAg, anti-HCV, and anti-HIV1-2/p24 Ag with those obtained using the VITROS system currently adopted by the Microbiology Unit of the Hospital of Legnano. Routine samples of patients who were referred by practitioners for the determination of HBsAg (1,000 samples) and/or anti-HCV (1,002 samples) and/or anti-HIV1-2 (995 samples) were simultaneously analyzed using both systems. The concordant positive and discordant samples were re-examined for confirmation by means of an HBsAg neutralization assay, anti-HCV immunoblot, or anti-HIV1-2 Western blot; HBV-DNA, or HCV-RNA or HIV-RNA was also sought in the discordant samples. Samples of patients known to be positive were tested (100 HBsAg positive, 100 anti-HCV positive, and 100 HIV 1-2 positive) as well throughout treatment, with viremia levels becoming undetectable after treatment. The HBsAg, anti-HCV, and anti-HIV1-2 concordance between the two systems in routine series was respectively 99.8%, 98.5% and 99.7%, and 100% for all markers in samples known positive. The various molecular biology and confirmatory tests of the discordant samples were all negative (except for one anti-HCV positive sample). Measure of Cohen's kappa coefficient for HBsAg, anti-HCV, and anti-HIV gave K values of respectively 0.992, 0.946, and 0.980. In conclusion, the performance of the LIAISON® XL system in the routine laboratory determination for all three markers was comparable with that of the VITROS system. J. Med. Virol. 89:489-496, 2017. © 2016 Wiley Periodicals, Inc.