Analytical Performance Characteristics and Clinical Utility of a Novel Assay for Total Hepatitis C Virus Core Antigen Quantification

Abstract

The detection and quantification of hepatitis C virus (HCV) core antigen in serum or plasma by the use of different assay formats have previously been shown to represent useful markers of viral replication. In the present study, the intrinsic performance characteristics and the potential clinical utility of a novel assay for the quantification of total HCV core antigen were comprehensively assessed by using clinical serum samples and specimens contained in various evaluation panels. The Architect HCV Ag assay showed a specificity of 100%. The intra-and interassay coefficients of variation ranged from 3.6 to 8.0% and from 4.7 to 9.5%, respectively. Except for HCV genotype 2 isolates, the analytical sensitivity was always less than 10 fmol core antigen/liter, corresponding to approximately 500 to 3,000 IU of HCV RNA/ml. Linearity was guaranteed throughout the dynamic range (10 to 20,000 fmol/liter). When seroconversion panels were tested, the assay was not inferior to HCV RNA detection and reduced the preseroconversion period by 4 to 16 days. The results obtained by core antigen and HCV RNA quantification for 385 clinical specimens were correlated by regression analysis (r ‫؍‬ 0.857), but the calculated conversion equation differed significantly from the line of identity. Monitoring of viral kinetics by use of either core antigen or RNA concentrations in 38 HCV-infected patients undergoing antiviral combination therapy resulted in very similarly shaped curves in all cases. Finally, the Architect HCV Ag assay was also shown to enable high-throughput screening of in vitro HCV RNA replication. With these results taken together, the Architect HCV Ag assay proved to be a specific, reproducible, highly sensitive, and clinically applicable test format which will find its future place in the context of virological HCV diagnostics.The virological diagnosis of infection with the hepatitis C virus (HCV) is based on the detection of specific anti-HCV antibodies. Since anti-HCV immunoassays, however, cannot distinguish between acute, past, and persistent infections, screening for HCV RNA is currently regarded as the method of choice for the confirmation of an active infection in both immunocompetent patients who are anti-HCV positive and immunocompromised individuals who may not mount an adequate antibody response (9,27,35,41).Assays for the amplification of HCV RNA are expensive and time-consuming and require sophisticated technical equipment and highly trained personnel. These constraints, however, do not apply to the detection of HCV core antigen, which is easy to perform in an immunoassay format, provides results in a comparably short time frame, and, theoretically, is less prone to sample carryover and, hence, contamination than assays based on nucleic acid amplification (17). During the past decade, therefore, several HCV core antigen tests were developed as potential alternatives to HCV RNA testing (1,4,43). The use of these assays in clinical laboratory settings documented that HCV core antigen can be detected in the s...

Comparison of a Newly Developed Automated and Quantitative Hepatitis C Virus (HCV) Core Antigen Test with the HCV RNA Assay for Clinical Usefulness in Confirming Anti-HCV Results

“…This need for retesting is a disadvantage of the HCV RNA test. In addition, nucleic acid amplifications are labor-intensive and time-consuming methods and have the risk of laboratory contamination; for these reasons, amplification methods are not suitable for widespread use in most laboratories, especially in developing countries (1,4,11,23,27). Therefore, the HCV Ag assay is needed as a supplemental or preconfirmatory test to preconfirm anti-HCV results and distinguish false-positive results from the accurate ones because it is easy to perform and reliable, has high specificity and sensitivity rates, is cost-effective, is able to shorten the duration of the time to diagnosis of infection in patients during the window period, and has a lower risk of laboratory contamination than assays based on nucleic acid amplification technology (31,28).…”

“…If both retest values indicate that the specimen is nonreactive, the specimen is considered nonreactive for HCV Ag. If one or both of the duplicates have values of Ն3.00 fmol/liter, the specimen is considered repeatedly reactive (16,23).…”

Evaluation Of An Enzyme Immunoassay For Hepatitis C Virus Core Antigen As A Diagnostic Test For Detection Of Hepatitis C Virus Infection In Comparison To Real-Time RT-PCR

“…The present study focused on the evaluation of the HCV cAg in relation to HCV RNA by real-time RT-PCR, thus we could not assess the effect of antiviral therapies on levels of HCV cAg and this agreed with (Ross et al, 2010), while Veillon et al (2003), concluded that the total HCV cAg assay is a useful test for the detection of HCV viremia and the monitoring of patients treated with IFN alone or in combination with ribavirin.…”

An Overview of the Laboratory Assay Systems and Reactives Used in the Diagnosis of Hepatitis C Virus (HCV) Infections

“…It is time consuming and expensive. 18,38 HCV RNA is extensively used to confirm antibodybased screening test results. Amplification methods (target amplification by RT-PCR, transmission-mediated amplification (TMA), and signal amplification by b-DNA-branch-DNA are the most expensive methods (45-50 USD per test for real-time PCR, 10-12 USD per test for HCV Ag CIA, and 5-6 USD per test for anti-HCV CIA) when compared with anti-HCV and HCV Ag tests; and require sophisticated technical equipment and highly trained personnel.…”

“…for these reasons, amplification methods are not suitable for wide use in most laboratories, especially in developing countries. 2,10,24,38,44 HCV Genotyping assay. HCV has six genotypes represented by digits (1-6) and multiple subtypes represented by letters (a, b, c…) and most recently a seventh HCV genotype have been characterized.…”