Clinical evaluation of the signal‐to‐cutoff ratios of hepatitis C virus antibody screening tests used in China

Abstract

The clinical diagnosis of hepatitis C virus (HCV) infection is important to direct an accurate course of therapy. Previous studies have reported a correlation between the signal-to-cutoff (S/CO) ratios of the anti-HCV screening test and confirm HCV infections for American anti-HCV screening kits as well as for those in China. It is currently unknown whether clinical laboratories use the same threshold S/CO ratios under routine conditions and if these values are acceptable for the analysis of Chinese samples. A total of 336 anti-HCV screening-test-positive serum samples were tested in duplicate using different lots of three most commonly used enzyme immunoassay (EIA) kits available in China. Samples were also tested using the Architect Anti-HCV chemiluminescent microparticle immunoassay (CMIA) kit and measured for HCV RNA. Recombinant immunoblot assays (RIBA) were additionally performed on samples with HCV RNA-negative results with RIBA HCV 3.0. The relationship between S/CO ratios and confirmed HCV infection rates were analyzed. The threshold S/CO ratio for each screening kit correlated with the ≥ 95% positive predictive value was InTec 12.0, KHB 4.0, Wantai 5.0, and Abbott Architect 5.0. Therefore, the same threshold S/CO ratios for manufactured domestically EIA kits was difficult to attain. A multi-center study with a large sample size is required to identify a uniform threshold S/CO ratio for use in different diagnostic laboratories. Alternatively, individual laboratories may be required to establish threshold S/CO ratios in their own laboratories to obtain consistent diagnostic results.

Genotype Distribution and Molecular Epidemiology of Hepatitis C Virus in Hubei, Central China

“…We speculated that the low prevalence of HCV RNA among anti-HCV-positive patients could be due to the high false-positive rate of the used assay for anti-HCV (Architect reagents). With this method, false-positive results have been found in about 95% of the initial positive results with S/CO values less than 5 [ 25 ], which accounted for around one third (185/570) of the subjects recruited in this study, indicating a low prevalence of HCV RNA in the cohort.…”

Comparison Between Screening and Confirmatory Serological Assays in Blood Donors in a Region of South Italy

“…In an attempt to ensure a higher PPV, higher thresholds for the S/CO values were considered. This approach has been employed in many previous studies on anti-HCV, and most of them have indeed demonstrated the relationship between high S/CO values and serological confirmation of anti-HCV positivity (9,(14)(15)(16)(17) and even with HCV viremia (14,18). Thus, a higher S/CO ratio for anti-HCV is deemed to guarantee a higher PPV, but the data on the other screening assays are less common (10,11,19), and we believe that ours is one of the first systematic attempts in this direction, although it has been carried out on a relatively small number of blood donations.…”

Reflex threshold of signal-to-cut-off ratios of the Elecsys anti-HCV II assay for hepatitis C virus infection

“…RIBA is still widely used in countries other than the United States due to its cost effectiveness [3][4][5]. In the present study, samples with an S/Co between 1 and 10 tested with Elecsys Anti-HCV II assay were mostly falsepositive by RIBA.…”

“…Current CDC guidelines suggest the use of assay-specific signal-to-cut-off (S/Co) ratios as anti-HCV confirmation to limit the number of samples needing supplemental testing [1,2]. Nevertheless, RIBA is still commonly used in other countries, including China [3][4][5].…”