Multicenter performance evaluation of the Elecsys HCV Duo immunoassay

Review of the U.S. Air Force Academy Hepatitis C Virus Screening Program to Ensure High-Value Care

INTRODUCTION

Hepatitis C virus (HCV) is primarily transmitted through blood-to-blood contact. Leading health agencies have called for the elimination of HCV as a public health threat, with universal screening considered a part of the strategy. Hepatitis C virus screening among incoming cadets and cadet candidates at the United States Air Force Academy (USAFA) was implemented in 2023. The purpose of this quality improvement project was to determine the results of this screening and the associated fiscal costs, benefits, and harms to make a recommendation for future incoming classes.

MATERIALS AND METHODS

The prevalence of HCV antibody positivity and confirmed HCV infections were calculated among the incoming cadets and cadet candidates at USAFA in summer 2023. Screening was conducted with a highly sensitive HCV total antibody test, and those who screened positive were further tested with a quantitative HCV polymerase chain reaction. The screening and follow-up care costs were calculated, and the potential harm of receiving a false positive notification was considered.

RESULTS

Of the 1,360 persons screened at USAFA in 2023, no confirmed HCV infections were identified. There was one false positive on screening in the cadet population (n = 1,131) and one false positive in the cadet candidate population (n = 229). The fiscal cost of universal HCV screening upon accession of cadets and cadet candidates, including medical follow-up, was at least $5,279. The opportunity cost was minimal because blood was drawn for other mandatory programs, although screening may have caused social and psychological harm to those receiving a false positive notification.

CONCLUSIONS

The prevalence of chronic HCV infection among incoming USAFA cadets and cadet candidates was 0%, below the population screening threshold that warrants screening, according to the Centers for Disease Control and Prevention. The harms of screening, including fiscal costs and potential psychological harm to individuals with a false positive screen, likely outweigh the benefits. We recommend against universal HCV screening in 2024 upon accession of USAFA cadets and cadet candidates.

Comparison of anti-HCV combined with HCVcAg (Elecsys HCV Duo immunoassay) and anti-HCV rapid test followed by HCV RNA analysis using qRT-PCR to identify active infection for treatment

Hepatitis C virus (HCV) infection can cause acute and chronic hepatitis, leading to liver cirrhosis and hepatocellular carcinoma. The World Health Organization aims to eliminate viral hepatitis by 2030 through extensive screening and treatment. To achieve this goal, comprehensive and widespread screening is essential for diagnosis and treatment. This study aims to evaluate the diagnostic sensitivity and specificity of the Elecsys® HCV Duo immunoassay (Duo-assay), which simultaneously detects anti-HCV antibodies (Duo/anti-HCV) and HCV core antigen (Duo/HCVcAg) in a single sample, compared with initially antibody testing followed by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, this study aimed to evaluate a relationship between Duo/HCVcAg and qRT-PCR assay in different genotypes. A total of 769 plasma samples were tested using the Duo-assay to further evaluate the test's performance and conduct Duo/HCVcAg correlation analysis using qRT-PCR for each genotype. Among the active infection group (anti-HCV+/RNA+; n = 473), the Duo-assay showed 100% sensitivity for detecting Duo/anti-HCV and 70.6% for Duo/HCVcAg. In the resolved infection group (anti-HCV+/RNA-; n = 176), the assay showed 100% sensitivity for Duo/anti-HCV and 100% specificity for Duo/HCVcAg. In the non-infected group (anti-HCV-/RNA-; n = 120), the assay showed 100% specificity for both Duo/anti-HCV and Duo/HCVcAg. Moreover, no correlation was observed between the Duo/HCVcAg and HCV RNA tests, irrespective of genotype. These findings indicate that the Duo-assay is highly sensitive for detecting anti-HCV and specifically identifies patients with active infection. Nevertheless, cases with anti-HCV+/HCVcAg-results should undergo additional confirmation with western blot/immunoblot and qRT-PCR to ensure diagnostic accuracy, especially in Blood donation facilities.

Comparison of a dual antibody and antigen HCV immunoassay to standard of care algorithmic testing

The Centers for Disease Control and Prevention (CDC) guidelines for hepatitis C virus (HCV) testing, although effective, may miss crucial diagnostic opportunities. The goal of this study was to assess the utility of an antibody (Ab) and antigen (Ag) combination immunoassay as an alternative to traditional HCV screening. Remnant specimens from 1,341 patients with concurrent third-generation serologic (Roche anti-HCV-II) and nucleic acid amplification testing (NAAT) were assessed using the HCV Duo Ab/Ag immunoassay (Roche). Patient demographics, risk factors, and standard of care (SOC) laboratory results from the medical records were recorded. Overall, 99.0% (197/199) of the HCV Duo Ab+/Ag+specimens accurately identified active infections as confirmed by NAAT, and 99.9% (670/671) Ab-/Ag- samples corresponded to those without HCV infections. Individually, the HCV Duo Ab component demonstrated a 95.6% positive percent agreement (PPA) (95% CI = 93.8-96.9) and 99.1% negative percent agreement (NPA) (98.8-99.6) compared with SOC anti-HCV II Ab assay. The HCV Duo Ag had a 73.5% PPA (67.9-78.4) and 99.8% NPA (99.3-100) with NAAT. Among RNA+ specimens, 73.4% (197/267) were HCV Duo Ag+, and 265/267 (99.3%) were successfully detected on the HCV Duo Ab component. Notably, 5/7 (71.4%) Ab-/RNA +specimens were detected by HCV Duo, which would have been missed by traditional algorithmic testing. Fourth generation HCV Duo Ab/Ag assay demonstrated comparable performance to SOC testing and shortens the diagnostic window but does not eliminate the need for NAAT in all patients. Ab/Ag testing identified several Ab-/RNA+ cases, a subgroup often undiagnosed by current algorithmic testing, demonstrating promise for improved diagnostic efficiency and accuracy in HCV detection.IMPORTANCEThis study highlights the potential of a combined hepatitis C virus (HCV) Duo antibody (Ab) and antigen (Ag) immunoassay to improve early detection of HCV infections. Traditional Ab-only screening methods recommended by the Centers for Disease Control and Prevention may miss early-stage infections. The HCV Duo assay showed high accuracy, detecting nearly all active infections confirmed by nucleic acid amplification testing. Dual detection of HCV Ab and Ag shortens the diagnostic window, enabling intervention and treatment in a single visit, which is crucial for improving patient outcomes and reducing HCV transmission, especially in areas with limited access to confirmatory molecular testing.

Performance of Elecsys® HCV Duo Immunoassay for Diagnosis and Assessment of Treatment Response in HCV Patients with or without HIV Infection

BACKGROUND/OBJECTIVES

The Elecsys® HCV Duo immunoassay (Roche Diagnostics International Ltd., Rotkreuz, Switzerland) detects both antibodies to hepatitis C virus (anti-HCV) and HCV core antigen (HCV-Ag) and has shown excellent diagnostic performance in blood donor samples. We aim to validate its use for diagnosing chronic HCV infection and assessing sustained virological response (SVR) post-direct-acting antivirals (DAAs) in patients with or without HIV infection.

METHODS

Blood samples from 100 healthy controls, as well as 64 HCV mono-infection and 136 HCV-HIV coinfections, were collected before and 12-24 weeks after DAAs. The assay performance for determining active infection at baseline and SVR was compared with HCV RNA.

RESULTS

Overall, 156 (78.0%) of HCV-infected patients had HCV genotype 1, and the SVR rate was 96.5%. The sensitivity, specificity, and area under the ROC curve (AUROC) for HCV diagnosis at baseline were 99.50% (95% confidence interval [CI], 96.82-99.97%), 100% (95%CI, 95.39-100%), and 0.998 (95%CI, 0.992-1.003), respectively. The corresponding results for HCV-Ag in determining SVR were 57.14% (95%CI, 20.24-88.19%), 97.41% (95%CI, 93.73-99.04%), and 0.773 (95%CI, 0.543-1.003), respectively. The assay also exhibited comparable sensitivity and specificity between HCV mono- and coinfection.

CONCLUSIONS

Our study showed that the Elecsys® HCV Duo immunoassay effectively diagnosed HCV infection, regardless of HIV status, making it suitable for managing high-risk populations in resource-limited settings.

Glycylglycine promotes the solubility and antigenic utility of recombinant HCV structural proteins in a point-of-care immunoassay for detection of active viremia

BACKGROUND

Although E. coli is generally a well-opted platform for the overproduction of recombinant antigens as heterologous proteins, the optimization of expression conditions to maximize the yield of functional proteins remains empirical. Herein, we developed an optimized E. coli (BL21)-based system for the overproduction of soluble immunoreactive HCV core/envelope proteins that were utilized to establish a novel immunoassay for discrimination of active HCV infection.

METHODS

The core/E1-E2 genes were amplified and expressed in E. coli BL21 (DE3) in the absence/presence of glycylglycine. The antigenic performance of soluble proteins was assessed against 63 HCV-seronegative (Ab-) sera that included normal and interferent sera (HBV and/or chronic renal failure), and 383 HCV-seropositive (Ab+) samples that included viremic (chronic/relapsers) and recovered patients' sera. The color intensity (OD450) and S/Co values were estimated.

RESULTS

The integration of 0.1-0.4M glycylglycine in the growth media significantly enhanced the solubility/yield of recombinant core and envelope proteins by ~ 225 and 242 fold, respectively. This was reflected in their immunoreactivity and antigenic performance in the developed immunoassay, where the soluble core/E1/E2 antigen mixture showed 100% accuracy in identifying HCV viremic sera with a viral RNA load as low as 3800 IU/mL, without cross-reactivity against normal/interferent HCV-Ab-sera. The ideal S/Co threshold predicting active viremia (> 2.75) showed an AUC value of 0.9362 (95% CI: 0.9132 to 0.9593), with 87.64, 91.23% sensitivity and specificity, and 94.14, 82.11% positive and negative predictive values, respectively. The different panels of samples assayed with our EIA showed a good concordance with the viral loads and also significant correlations with the golden standards of HCV diagnosis in viremic patients. The performance of the EIA was not affected by the immunocompromised conditions or HBV co-infection.

CONCLUSION

The applicability of the proposed platform would extend beyond the reported approach, where glycylglycine, low inducer concentration and post-induction temperature, combined with the moderately-strong constitutive promoter enables the stable production of soluble/active proteins, even those with reported toxicity. Also, the newly developed immunoassay provides a cost-effective point-of-care diagnostic tool for active HCV viremia that could be useful in resource-limited settings.