Evaluation of a hepatitis C virus core antigen assay from venepuncture and dried blood spot collected samples: A cohort study

Hepatitis C Virus-Core Antigen: Implications in Diagnostic, Treatment Monitoring and Clinical Outcomes

The hepatitis C virus (HCV) infection, a global health concern, can lead to chronic liver disease. The HCV core antigen (HCVcAg), a viral protein essential for replication, offers a cost-effective alternative to HCV RNA testing, particularly in resource-limited settings. This review explores the significance of HCVcAg, a key protein in the hepatitis C virus, examining its structure, function, and role in the viral life cycle. It also evaluates its clinical use in diagnosis and treatment monitoring, comparing its performance to the standard HCV RNA assay using data from PubMed and Google Scholar. HCVcAg assays show high pooled sensitivity (93.5%) and pooled specificity (99.2%) compared to HCV RNA assays, correlating closely (r = 0.87) with HCV RNA levels. Hence, HCVcAg testing offers a cost-effective way to diagnose active HCV infections and monitor treatment, especially in resource-limited settings, but its sensitivity can vary and standardization is needed. HCVcAg also predicts liver disease progression and assesses liver damage risk, aiding patient management. It helps to identify patients at risk for fibrosis or carcinoma, making it vital in hepatitis C care. HCVcAg testing can expand access to HCV care, simplify management, and contribute to global elimination strategies, especially in low- and middle-income countries.

Diagnostic performance of dried blood spot hepatitis C virus core antigen testing for hepatitis C screening: A systematic review and meta-analysis

Dried blood spot (DBS) sampling is increasingly used for hepatitis C virus (HCV) screening. HCVcAg testing offers a faster and more streamlined approach to diagnosing HCV infection. We conducted a systematic review and meta-analysis to assess the diagnostic performance of the Abbott ARCHITECT HCV Ag assay for screening active HCV infection using DBS samples. Eight studies (n = 1229) were selected among all published studies available up to October 4, 2024, in different databases with a search strategy registered (PROSPERO: CRD42022363975). The gold standard method was the HCV PCR test. Data were analyzed using the MIDAS module in STATA with a random effects model. Combined diagnostic accuracy measures were as follows: sensitivity 85%, specificity 100%, positive likelihood ratio (PLR) 233.1, negative likelihood ratio (NLR) 0.15, and summary receiver operating characteristic (SROC) 0.99. Likelihood ratios and Fagan's nomogram suggested that the HCVcAg assay with DBS samples can confirm or rule out active HCV infection with over 92% accuracy in high-prevalence settings (≥5%). However, in low-prevalence settings (≤1%), a confirmatory test must be required for positive results. The ability of the test to identify people without HCV infection was high regardless of HCV prevalence, with an error rate of less than 3%. This meta-analysis is subject to limitations, particularly due to the number of included studies and significant heterogeneity among them. HCV screening using the Abbott ARCHITECT HCV Ag assay with DBS samples showed excellent diagnostic performance, but its external validity may be limited when HCV prevalence is low (≤1%).

A novel test and treat program for hepatitis C virus infection utilizing HCV core antigen testing, among police and general population, Islamabad, Pakistan, 2022

Hepatitis C virus core antigen (HCVcAg) testing can simplify and decrease costs of HCV infection confirmation compared to molecular testing (nucleic acid testing). We piloted HCVcAg testing for the confirmation of active infection. The study was conducted during June through December 2022 among the police and the general population of Islamabad, Pakistan age 18 years and older. Initial screening for HCV antibody was conducted using a rapid diagnostic test (RDT) for all consenting participants. Those who tested positive had venous blood samples tested for HCVcAg, platelets and aspartate aminotransferase (AST). Persons with HCVcAg values ≥3 fmol/L were defined as viremic, and they were offered treatment with direct acting antiviral (DAA) medications, sofosbuvir and daclatasvir. Aspartate aminotransferase to platelet ratio index (APRI) was calculated for each HCV infected person, and those with an APRI score <1.5 received treatment for 12 weeks, while those with APRI ≥ to 1.5 received 24 weeks of treatment. A total of 15,628 persons were screened for anti-HCV using RDT and 643 (4.1%) tested positive. HCVcAg values of ≥3 fmol/L was found in 399/643 (62.1%), and all were offered and accepted treatment. Of those treated, 273/399 (68.4%) returned for a follow-up SVR and HCVcAg was not detected in 261/273, a 95.6% cure rate. The pilot study demonstrated the effectiveness of reaching and treating an urban population using RDT for screening and HCVcAg for confirmation of infection and test of cure.

Hepatitis C

Hepatitis C virus (HCV) is a hepatotropic RNA virus that can cause acute and chronic hepatitis, with progressive liver damage resulting in cirrhosis, decompensated liver disease, and hepatocellular carcinoma. In 2016, WHO called for the elimination of HCV infection as a public health threat by 2030. Despite some progress, an estimated 57 million people were living with HCV infection in 2020, and 300 000 HCV-related deaths occur per year. The development of direct-acting antiviral therapy has revolutionised clinical care and generated impetus for elimination, but simplified and broadened HCV screening, enhanced linkage to care, and higher coverage of treatment and primary prevention strategies are urgently required.

Impact of storage time in dried blood samples (DBS) and dried plasma samples (DPS) for point-of-care hepatitis C virus (HCV) RNA quantification and HCV core antigen detection

The scale-up of hepatitis C virus (HCV) diagnosis and treatment requires affordable and simple tools to improve access to care, especially in low- and middle-income settings with limited infrastructure or high-risk populations. Dried blood and plasma samples (DBS and DPS) are useful alternative for hepatitis C detection in settings lacking adequate infrastructure. We evaluated the performance of DBS and DPS vs plasma in a point-of-care HCV RNA quantitative assay (Xpert HCV Viral Load-Cepheid), and compared HCV core antigen (HCVcAg) detection by the Architect HCV core antigen assay (Abbott) in DBS vs serum. The dried samples were stored at room temperature for different storage times to reproduce the time from sampling to testing in settings with centralized diagnosis or when testing mobile populations. HCV RNA quantification in DBS and DPS presented 100% sensitivity and specificity and a high correlation for up to 3 months of storage. HCV viremia showed a mean decrease of 0.5 log10 IU/mL (DBS) and 0.3 log10 IU/mL (DPS) for storage times up to 1 month. Architect HCVcAg detection presented high sensitivity/specificity (96%/100%) in DBS tested immediately after sampling, decreasing to 86% sensitivity after 7 days of storage. However, sensitivity increased when an optimized cut-off was applied for each storage time. We conclude that DBS and DPS are suitable samples for HCV RNA detection and quantification, being DPS more reliable for shorter storage times. DBS can be also used for HCVcAg qualitative detection and the sensitivity can be increased when adjusting the cut-off values. IMPORTANCE Hepatitis C infection remains a global burden despite the effectiveness of antivirals. In the WHO roadmap to accomplish HCV elimination by 2030, HCV diagnosis is one of the main targets. However, identifying patients in resource-limited settings and high-risk populations with limited access to healthcare remains a challenge and requires innovative approaches that allow decentralized testing. The significance of our research is in verifying the good performance of dried samples for HCV diagnosis using two different diagnostics assays and considering the effect of room temperature storage in this sample format. We confirmed dried samples are an interesting alternative for HCV screening and reflex testing in resource-limited settings or high-risk populations.

Diagnostic performance of hepatitis C core antigen assay to identify active infections: A systematic review and meta-analysis

Hepatitis C virus (HCV) core antigen (HCVcAg) assay is an alternative for diagnosing HCV infection in a single step. This meta-analysis aimed to evaluate the Abbott ARCHITECT HCV Ag assay's diagnostic performance (validity and utility) for diagnosing active hepatitis C. PubMed, EMBASE, Scopus, Web of Science, and Cochrane Library were searched until 10 January 2023. The protocol was registered at the prospective international register of systematic reviews (PROSPERO: CRD42022337191). Abbott ARCHITECT HCV Ag assay was the test for evaluation, and nucleic acid amplification tests with a cut-off ≤50 IU/mL were the gold standard. Statistical analysis was performed using STATA with the MIDAS module and random-effects models. The bivariate analysis was conducted on 46 studies (18,116 samples). The pooled sensitivity was 0.96 (95% CI = 0.94-0.97), specificity 0.99 (95% CI = 0.99-1.00), positive likelihood ratio 141.81 (95% CI = 72.39-277.79), and negative likelihood ratio 0.04 (95% CI = 0.03-0.06). The area under the summary receiver operating characteristic curve was 1.00 (95% CI = 0.34-1.00). For active hepatitis C prevalence values of 0.1%-15%, the probability that a positive test was a true positive was 12%-96%, respectively, indicating that a confirmatory test should be necessary, particularly with a prevalence ≤5%. However, the probability that a negative test was a false negative was close to zero, indicating the absence of HCV infection. The validity (accuracy) of the Abbott ARCHITECT HCV Ag assay for screening active HCV infection in serum/plasma samples was excellent. Although the HCVcAg assay showed limited diagnostic utility in low prevalence settings (≤1%), it might help diagnose hepatitis C in high prevalence scenarios (≥5%).

Longitudinal assessment of HCV core antigen kinetics to monitor therapeutic response in the age of DAAs

BACKGROUND

In the economy of therapeutic monitoring, an affordable viral marker is essential in the era of direct-acting antivirals (DAAs). We elucidated the kinetics of HCVcAg to delineate its precise role in monitoring therapeutic response.

METHODS

In this longitudinal study, 3208 patients were tested for HCV RNA. A total of 423 patients were started on DAAs. Treatment response and kinetics of HCVcAg/RNA were assessed in treatment-naïve (n = 383) and previously treated (n = 40) patients with follow-up for 2 years.

RESULTS

After the initiation of DAAs, the rate of relapse was significantly higher in the previously treated group than naive group [12.5% (5/40) Vs 2% (7/383), p<0.0001]. The response rate at RVR was significantly higher with HCVcAg than RNA in both groups (p<0.02). The kinetics of HCVcAg and RNA were significantly different at ETR and SVR12 in the naïve (p<0.04), but similar at all therapeutic points in the previously treated group. The correlation between HCVcAg and RNA was good at baseline, ETR and SVR, except RVR in both groups (r>0.6; p<0.0001). Furthermore, HCV genotypes, treatment regimen, CTP (<7/≥7) and MELD (<15/≥15) did not influence the therapeutic response and the viral replication kinetics (p>0.05).

CONCLUSIONS

It is the first longitudinal study from India shows that the response rate and kinetics of HCVcAg are comparable to HCV RNA for an extended duration, except at RVR, irrespective of the HCV genotypes, treatment regimen, and liver disease severity. Hence, HCVcAg can be considered as a pragmatic marker to monitor therapeutic response and predict relapse in the era of DAAs.

Comparing RT-qPCR and Hepatitis C Virus Antigen Detection Assay for Detecting Active Infection in Blood Donors in Fars Province, Iran

Background: Immunoassay is still used to detect hepatitis C virus (HCV) antibodies in donated blood in many developing countries. However, an immunoblotting confirmation test is needed to confirm positive results. Objectives: We compared the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of nucleic acid testing and HCV core antigen (HCVcAg) detection in the serum samples of blood donors with HCV antibodies to determine active infection. Methods: Overall, 90 serum samples from blood donors referred to Fars Blood Transfusion Organization, Iran during March 2017-March 2019 and initially tested for HCV antibodies were included in the study. Enzyme immunoassays were used to detect the HCV antigen and anti-HCV antibody. A commercial reverse transcription-polymerase chain reaction (RT-PCR) kit was used to quantify HCV RNA. The HCV genotypes were also determined by DNA sequencing. In order to compare the HCVcAg detection method with the RT-qPCR reference method, sensitivity, specificity, performance, PPV, and NPV were calculated. Results: Out of 90 serum samples, 73 were positive for anti-HCV antibody, and 17 sera were negative. The HCV RNA was detected in 60 (82%) of anti-HCV antibody-positive samples, whereas the HCVcAg test detected HCV antigen in 54 (74%) of the samples, indicating a significant correlation between the two assays (r = 0.86). The overall sensitivity and specificity for HCVcAg detection method were 93.85% [95% confidence interval (CI): 84.99 - 98.3%] and 100% (95% CI: 94.64 - 100%), respectively. Based on the statistical analysis, the accuracy of the antigen detection test was 94.83% (95% CI: 87.26 - 98.58%). Moreover, the agreement between HCV RNA detection using RT-qPCR and HCVcAg detection was 97.78% (kappa value: 0.94). Conclusions: The sensitivity and specificity of HCVcAg detection in blood donors were ideal compared to the RT-qPCR reference method. However, the method should be tested on more HCV antibody-positive and -negative samples. Furthermore, our study revealed a significant association between the number of RT-qPCR-positive cases and the cases diagnosed by the HCVcAg detection method for screening and detecting active HCV infection in blood donors.

Economic evaluation of pan-genotypic generic direct-acting antiviral regimens for treatment of chronic hepatitis C in Iran: a cost-effectiveness study

INTRODUCTION

Low-cost generic direct-acting antiviral (DAA) regimens for treatment of hepatitis C virus (HCV) are available in several low-income/middle-income countries, important for treatment scale-up. This study evaluated the cost-effectiveness of genotype-dependent and pan-genotypic DAA regimens in Iran as an example of a resource-limited setting.

METHODS

A Markov model was developed to simulate HCV natural history. A decision tree was developed for HCV treatment, assuming four scenarios, including scenario 1: genotyping, sofosbuvir/ledipasvir (SOF/LDV) for genotype 1, and sofosbuvir/daclatasvir (SOF/DCV) for genotype 3; scenario 2: genotyping, SOF/LDV for genotype 1, and sofosbuvir/velpatasvir (SOF/VEL) for genotype 3; scenario 3: no genotyping and SOF/DCV for all; and scenario 4: no genotyping and SOF/VEL for all. A 1-year cycle length was used to calculate the cumulative cost and effectiveness over a lifetime time horizon. We calculated quality-adjusted life years (QALYs), and incremental cost-effectiveness ratio (ICER) using a health system perspective. Costs were converted to US dollars using purchasing power parity exchange rate ($PPP). All costs and outcomes were discounted at an annual rate of 3%.

RESULTS

Among people with no cirrhosis, scenario 3 had the minimum cost, compared with which scenario 4 was cost-effective with an ICER of 4583 $PPP per QALY (willingness-to-pay threshold: 9,311 $PPP per QALY). Among both people with compensated or decompensated cirrhosis, scenario 4 was cost saving. In sensitivity analysis, scenario 4 would be also cost-saving among people with no cirrhosis provided a 39% reduction in the cost of 12 weeks SOF/VEL.

CONCLUSION

Initiating all patients on pan-genotypic generic DAA regimens with no pretreatment genotyping was cost-effective compared with scenarios requiring pretreatment HCV genotype tests. Among generic pan-genotypic DAA regimens, SOF/VEL was cost-effective, for people with no cirrhosis and cost-saving for those with cirrhosis.

Performance of HCV Antigen Testing for the Diagnosis and Monitoring of Antiviral Treatment: A Systematic Review and Meta-Analysis

BACKGROUND AND AIMS

Active hepatitis C virus (HCV) infection is based on the detection of HCV RNA that it is effective but presents high cost and the need to hire trained personnel. This systematic review and meta-analysis is aimed at evaluating the diagnostic accuracy of HCV Ag testing to identify HCV cases and to monitor antiviral treatment including DAA treatment.

METHODS

The studies were identified through a search in PubMed, Lilacs, and Scopus from 1990 through March 31, 2020. Cohort, cross-sectional, and randomized controlled trials were included. Two independent reviewers extracted data and assessed quality using an adapted Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Our primary outcome was to determine the accuracy of HCV Ag detection for the diagnosis, which we estimated using random-effects meta-analysis.

RESULTS

Of 3,062 articles identified, 54 met our eligibility criteria. The studies described cohorts from 20 countries, including 14,286 individuals with chronic HCV individuals. Studies for ECLIA technology demonstrated highest quality compared to studies that used ELISA. The pooled sensitivity and specificity (95% CI) for HCV Ag detection of active HCV infection were 98.82% (95%CI = 98.04%; 99.30%) and 98.95% (95%CI = 97.84%; 99.49%), respectively. High concordance was found between HCV Ag testing and HCV RNA detection 89.7% and 95% to evaluate antiviral treatment.

CONCLUSIONS

According to our findings, HCV Ag testing could be useful to identify HCV active cases in low-resource areas. For antiviral treatment, HCV Ag testing will be useful at the end of treatment.

Laboratory-based testing for hepatitis C infection using dried blood spot samples: A systematic review and meta-analysis of diagnostic accuracy

The use of dried blood spot (DBS) samples can facilitate the implementation of reflex testing by circumventing the need for centrifugation and freezing of venous blood samples. This systematic review assessed the accuracy of using DBS samples to diagnose chronic hepatitis C virus (HCV) infection. A comprehensive search was undertaken to identify articles published up to July 2020 evaluating the diagnostic accuracy of anti-HCV, HCV-RNA and HCV core antigen tests using DBS. Screening, data extraction, quality appraisal and Grading of Recommendations, Assessment, Development and Evaluations certainty of the evidence assessment were performed independently by two reviewers. Meta-analysis, meta-regression and sensitivity analyses were conducted. The evidence demonstrates that laboratory-based anti-HCV and HCV-RNA tests using DBS samples have high diagnostic accuracy. All comparisons were between DBS and venous samples. For the detection of anti-HCV, sensitivity was 95% (95% CI: 92%-97%) and specificity was 99% ([95% CI: 98%-99%]; n = 25; I²  = 81%; moderate certainty). For the detection of HCV-RNA, the sensitivity was 95% (95% CI: 93%-97%) and specificity was 97% ([95% CI: 94%-98%]; n = 20; I²  = 52%; moderate certainty). The sensitivity of HCV core antigen tests was 86% (95% CI: 79%-91%) and specificity was 98% ([95% CI: 94%-99%]; n = 5; I²  = 37%; low certainty) compared with HCV-RNA (the gold standard for detecting chronic HCV). DBS samples could facilitate diagnosis of chronic HCV infection as the necessary sequential tests (anti-HCV and then HCV-RNA or HCV core antigen) can be undertaken using the same blood sample. This could reduce loss of patient follow-up and support international efforts towards HCV elimination in both high and low prevalence settings.

Evaluation of Hepatitis C Virus Core Antigen Assay in a Resource-Limited Setting in Pakistan

The diagnosis of Hepatitis C virus (HCV) infection can be challenging due to its cost and a lack of access to centralized testing. There is an urgent need to develop simplified HCV testing algorithms. The aim of this study was to evaluate the performance characteristics of a Hepatitis C core antigen (HCVcAg) assay in a decentralized, resource-limited setting. This is a descriptive cross-sectional study from a highly endemic area of Karachi, Pakistan. Between October 2019 and July 2020, subjects aged 12 years and above who screened positive for HCV antibodies were simultaneously tested for HCV RNA (Xpert HCV Viral Load, GeneXpert^® IV, Cepheid, France) and HCVcAg (ARCHITECT HCV Ag assay, Abbott^® Diagnostics) to confirm active HCV infection. An Abbott ARCHITECT^® i1000SR Immunoassay Analyser was installed at a local district hospital as a point-of-care (POC) facility for HCVcAg testing, while samples for HCV RNA were tested in a central lab. Two hundred individuals (mean age 46.4 ± 14.5 years, 71.5% females), who screened positive for HCV antibody, were included in the study. HCV RNA was detected in 128 (64.0%) while HCVcAg was reactive in 119 (59.5%) cases. Performance of the Immunoassay Analyser was excellent with a higher throughput and quicker readout value compared to the GeneXpert System. The sensitivity and specificity of HCVcAg (≥10 fmol/L) at HCV RNA thresholds of ≥12 was 99.1% (95% CI: 95–100%) and 87.6% (95%CI: 78.4–94%). A strong agreement was observed between the HCVcAg assay and HCV RNA. The ARCHITECT HCV Ag assay showed high sensitivity and specificity compared to HCV RNA in a decentralized, resource-limited setting. It can therefore be used as a confirmatory test in HCV elimination programs, particularly for low-income countries such as Pakistan.

EASL recommendations on treatment of hepatitis C: Final update of the series☆

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease, with approximately 71 million chronically infected individuals worldwide. Clinical care for patients with HCV-related liver disease has advanced considerably thanks to an enhanced understanding of the pathophysiology of the disease, as well as developments in diagnostic procedures and improvements in therapy and prevention. These therapies make it possible to eliminate hepatitis C as a major public health threat, as per the World Health Organization target, although the timeline and feasibility vary from region to region. These European Association for the Study of the Liver recommendations on treatment of hepatitis C describe the optimal management of patients with recently acquired and chronic HCV infections in 2020 and onwards.

Real-world utility of HCV core antigen as an alternative to HCV RNA testing: Implications for viral load and genotype

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.