Abstract
Following positive serology, the gold standard confirmatory test of hepatitis C virus (HCV) infection is detection of HCV RNA by PCR. We assessed the utility of HCV core antigen testing to identify active infection among those positive for anti-HCV antibodies, when introduced to routine testing. We identified serum samples that were tested at a single laboratory in Scotland from June 2011to December 2017. Serum samples testing positive for HCV antibodies (HCV Ab positive) followed by reflex HCV core antigen (Ag) testing during the study period were identified. Those patients for whom a PCR test was requested on the baseline sample were also identified. For this group, the sensitivity and specificity of HCV Ag as a diagnostic tool were assessed using HCV PCR as gold standard. In our cohort of 744 patients, we demonstrated a sensitivity of 82.1% (95% CI 77.1%-86.2%) and a specificity of 99.8% (95% CI 98.6%-100%). Genotype 3 was associated with increased odds of a false-negative result (OR=3.59, 95% CI: 1.32-9.71), and reduced odds of a false negative were associated with older age (odds ratio (OR)=0.92, 95% CI: 0.88-0.97 per year) and viral load (OR=0.10, 95% CI: 0.05-0.21 per log10 IU/ml). While the implementation of HCV core antigen testing for diagnosis could lead to significant cost savings in national screening programmes, our data suggest that a significant proportion of HCV-infected individuals may be missed. These findings have implications for HCV diagnosis and determination of viral clearance after treatment, particularly in low- and middle-income regions, where genotype 3 is prevalent.
Highlights
Infection with hepatitis C virus (HCV) is a major cause of chronic liver disease worldwide, and it has been estimated that approximately 70 million people were chronically infected in 2016.1 In recent years, direct-acting antiviral (DAA) drugs for chronic HCV infection have been welcomed as an effective intervention in reducing HCV-related liver disease burden.[2,4]
The World Health Organisation (WHO) has provisionally accepted the ARCHITECT HCV core antigen (HCV Ag) assay as a pre-qualified in vitro diagnostic modality for the detection of newly acquired HCV infection.[23]
WHO recognizes several research gaps relating to HCV Ag
Summary
Infection with hepatitis C virus (HCV) is a major cause of chronic liver disease worldwide, and it has been estimated that approximately 70 million people were chronically infected in 2016.1 In recent years, direct-acting antiviral (DAA) drugs for chronic HCV infection have been welcomed as an effective intervention in reducing HCV-related liver disease burden.[2,4] a major barrier to HCV treatment and elimination 5 is low rates of testing and diagnosis, with large variations across different regions, countries and at-risk populations. The gold standard algorithm for diagnosis of HCV infection requires serologic testing for antibodies, and in those who are tested as being antibody-positive, further confirmation of viral replication by HCV RNA testing.[8] HCV core antigen testing, as an alternative to RNA testing, has the potential to reduce diagnostic costs, if it is both sensitive and specific enough without the need for supplementary PCR testing.[9] For cost reasons, HCV core antigen testing has been recommended for use in low- to middle-income countries (LMICs).[6] there are limited data on the performance of core antigen testing when introduced as routine testing and how this concomitantly links patients to appropriate clinical management. The WSSVC introduced reflex antigen testing as the standard diagnostic test to detect ongoing infection among HCV antibody-positive patients in NHS GG&C in 2011. Our principal objective was to estimate the sensitivity and specificity of HCV Ag using HCV RNA status from PCR testing as the gold standard
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