Rapid Core Antigen HCV Tests Could Expand Accessibility

Neil Osterweil

July 01, 2021

A proposed rapid diagnostic test for hepatitis C viral infections that combines an inexpensive but lower-sensitivity core-antigen test with lab RNA confirmation of negative tests could expand testing and same-day initiation of antiviral therapy in places where resources are limited, investigators said.

Applying the proposed method to the Republic of Georgia, with a hepatitis C virus (HCV) prevalence of 5.4% as reported by the World Health Organization, would result in a 95.4% diagnosis rate, compared with 78.8% for lab-based RNA testing, which is the standard of care. Applied to Malaysia, the proposed method would boost diagnosis rates from 57.0% to 91.2%, reported Madeline Adee, MPH, from Massachusetts General Hospital's Institute for Technology Assessment in Boston and colleagues.

"We found that a novel core antigen rapid diagnostic test for HCV could improve the diagnosis rate and result in cost savings. Although not yet developed, such a test could be a game changer and have a substantial impact on the feasibility and cost of HCV elimination, especially in low and middle-income countries," they wrote in a poster presented at the meeting sponsored by the European Association for the Study of the Liver.

Although rapid diagnostic tests for HCV can improve diagnosis and treatment rates, currently available molecular tests are expensive and require a solid clinical laboratory infrastructure, which can put such tests out of the reach for clinicians in low- or middle-income countries. Rapid immunoassays based on HCV core antigens are comparative bargains, but their sensitivity ranges from 70% to 90%; in contrast, the third-generation HCV enzyme immunoassay has about a 98% sensitivity.

Could It Work?

The proposed testing method would be likely to improve diagnosis, but whether that would translate into increased treatment is uncertain, commented Lesley Miller, MD, who specializes in HCV screening and treatment in underserved populations at Emory University, Atlanta.

"When we're talking about hepatitis C, it's all about the care cascade, the drop-off at each step from those who have the disease and aren't diagnosed, to those who are tested and only partially diagnosed because they don't have a confirmed infection, to those that get into care, get treated, and get cured," she said in an interview.

"It's all about closing the gaps in the care cascade in order to achieve elimination of the virus, which is what we're all trying to do," she added.

She pointed that there are certain at-risk populations in the United States, such as injectable-drug users, who might be able to benefit from such a system.

"These folks often have less access to traditional care, so bringing rapid testing and care to where those folks are is really important, so if we can deploy mobile units to areas where there is high prevalence and do it at the point of care, it simplifies the entire process," she said.

Thomas J. Hoerger, PhD, a senior fellow in health economics and financing at the nonprofit research group RTI International in Research Triangle Park, N.C., said in an interview that the proposed model could eliminate the step in testing in which patients are required to return for confirmation.

"People don't always come back for further testing, so if you can do it immediately and have the results of a screening test, you might be able to get people to come back more quickly. You still have the problem of the high cost of treatment, but this would at least make it a little more convenient," he said.

He noted that the success of the strategy would be dependent on the sensitivity of the rapid core antigen test, it's cost relative to HCV RNA testing, and whether the availability of the rapid test would translate into an improvement in follow-up.

Neither Miller nor Hoerger were involved in the study.

Evaluating the Approach

To determine whether a lower-cost rapid test could be cost effective, the researchers created a microsimulation model of the natural history of HCV to compare potential outcomes from either core antigen rapid diagnostic testing with a base case sensitivity for HCV viremia of 80% with lab-based RNA confirmation for negative results or the current standard of care with lab-based RNA confirmation only.

The model incorporated METAVIR stage F0-F4, decompensated cirrhosis, hepatocellular carcinoma, and liver-related death. The investigators determined the baseline characteristics of HCV patients in each country based on different distributions of sex, HCV genotype, and METAVIR fibrosis stage.

They simulated outcomes for 10,000 adults in the Republic of Georgia, with an HCV prevalence of 5.4%, and Malaysia, with an HCV prevalence of 1.5%.

The model considers costs from a health care payer's perspective, and the investigations performed deterministic and probabilistic sensitivity analyses to evaluate how the cost-effectiveness of testing pathways might change when various factors were plugged into the model.

As noted before, the investigators determined that the core antigen rapid test algorithm would improve diagnosis rates in Georgia from 78.8% to 95.4% and in Malaysia from 57.9% to 91.2%.

The use of the rapid test would also increase quality-adjusted life-years in Georgia by 207 per 10,000 and in Malaysia by 146 per 10,000.

Cost savings, primarily from averting the costs of care for patients with HCV, begin within the first year of the model. Over 50 years, the lifetime horizon cost savings in Georgia would be $232,000 per 10,000 people, and the corresponding savings in Malaysia would be $504,000 per 10,000 people.

Even when allowing for variations in parameters, the core antigen rapid diagnostic test approach remained the preferred model, the investigators reported.

The study was supported by the global health agency Unitaid. The researchers, Miller, and Hoerger reported no conflicts of interest relevant to the study.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.


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