Because of a significant increase in the number of hepatitis C virus (HCV)-related cases, efforts are being made to improve diagnostic tests available to clinicians. A study by Duke University, published in the December 2005 issue of Hepatology, found that HCV-related hospital visits increased more than 20% between 1994 and 2001.1
Stephen R. Lee
“There was a large reservoir of infection that accumulated in the population as a result of transmission back in the ’70s and ’80s through intravenous drug use and blood transfusions before the availability of blood testing,” says Stephen R. Lee, PhD, executive vice president and chief science officer, OraSure Technologies Inc. “So this disease is really just working its way through the health care system,” and the consequences could be epidemic. The Centers for Disease Control and Prevention (CDC) estimates that 2.7 million of the 3.9 million Americans infected with HCV are chronically infected.2 About 80% of the carriers have no signs or symptoms of the virus, which resides in and is transmitted through the blood.
According to the CDC, for every 100 people infected with HCV, roughly half could develop long-term infection; approximately 70% are at risk of developing chronic liver disease, and as many as 20% of those individuals might develop cirrhosis.3
A Growing Concern
As the numbers increase, “we become more and more aware of it and are becoming smarter at diagnosing and treating it,” says Nicholas Karyotakis, MD, chief scientific officer, gastrointestinal biosciences, and attending gastroenterologist at Cedars-Sinai Medical Center in Los Angeles.
“In recent years, treatment has evolved significantly. We now have access to more options, as well as better-tolerated treatments,” Karyotakis says. “The recommendation for treatment is pegylated interferon, which is a longer-acting formulation of interferon—used in combination with ribavirin, which is an antiretroviral drug.”
Even with such gains, there is much work to be done. Chronic hepatitis C has a well-characterized disease progression, making the ability to accurately—and regularly—-assess patients one of the biggest concerns for physicians.
“The histopathology of patients chronically infected with HCV changes over time,” says Eric Fung, MD, PhD, vice president of clinical affairs, Ciphergen. “The chronic infection leads to chronic inflammation, which leads to fibrosis, which worsens until eventually, the liver becomes cirrhotic.” A significant number of those patients will eventually develop cancer.
After the initial diagnosis, physicians have a handful of tools for monitoring the progression of HCV-related diseases, including liver biopsies and ultrasound exams.
“As you might suspect, the best way to monitor for liver pathology is to take a biopsy and look at the histopathology directly,” Fung says. “What’s being done predominantly is a combination of biopsy and ultrasound to visualize nodules, which are often a sign of cirrhosis.”
Neither method is without flaw. Ultrasound exams are limited by the size of visible nodules and can often be misleading, as not all nodules are cirrhosis or cancer. While considered by many to be the gold standard, biopsies are painful, expensive procedures with limited availability to physicians. The current recommendation is for the procedure to be performed no more than once every 3 years, during which time significant disease progression can occur. Perhaps most importantly, a biopsy provides only a narrow view of what is taking place in the organ.
“When you take a biopsy you’re only looking at about 1/50,000th of the liver, which means the section you look at may not be representative of everything going on in the liver,” Fung says. “You may find an area that looks fine, but in fact there might actually be fibrosis in a part of the liver you did not sample.”
Fung is currently involved in research to determine whether serum proteomics will be useful in helping assess this clinical issue. “The idea is that blood circulates throughout the entire body and, of course, throughout the entire liver, suggesting that whatever proteins are being changed as a result of the inflammation, and fibrosis, cirrhosis, or cancer will be represented in the blood,” he says. He adds that the goal is to develop a blood test that could provide clinicians with an accurate snapshot of the patient’s current level of health.
Blood Tests Increase Accessibility
A blood test for liver disease resulting from HCV infection would provide the clinician a method for assessing a patient’s status every few months, which could translate to catching more severe diseases in the earliest stages.
“One of the real fears with hepatitis C is the development of hepatocellular carcinoma, which can develop in people with cirrhosis,” says Ned Snyder, MD, professor of internal medicine, chief of clinical gastroenterology and hepatology, University of Texas Medical Branch (UTMB) in Galveston. Snyder regularly treats HCV patients and also works closely with the study team.
He adds that existing methods of testing, such as magnetic resonance imaging and ultrasound, simply do not provide the necessary level of detail. “Hepatocellular carcinoma is a highly aggressive, fast-growing tumor, and if we had a blood test that was a marker for the tumor—or for people most prone to developing the tumor—it would be very helpful clinically.”
For the past 3 years, Fung’s team has been working in collaboration with researchers at UTMB to tackle this specific challenge. Made possible through grants from the National Institutes of Health (NIH) and the National Institute of Allergy and Infectious Diseases (NIAID), the research would lead to “development of a proteomics chip using our thioaptamers to pull down specific proteins that can serve as biomarkers for infectious diseases such as hepatitis C,” says David Gorenstein, PhD, associate dean for research, school of medicine, Charles Marc Pomerat Distinguished Professor of Biological Sciences, UTMB. Created at UTMB, “thioaptamers—or, simply, aptamers—are oligonucleotides selected from large combinatorial libraries that have properties very much like antibodies, but the backbone is nucleic acid,” he says.
Starting From the Finish
The test’s basic concept is not entirely new. At press time, two noninvasive tests that measure a number of different clinical analytes to detect liver disease were commercially available, but Fung belives that both leave room for improvement.
“Both of these tests were derived based on known proteins—by taking a long list of analytes and combining them to create the index,” Fung says. He adds that this traditional approach relies heavily on making assumptions. Specific proteins are either included or excluded from an index based on a researcher’s understanding of the biological system or other preliminary clinical data.
Fung’s team is tackling the problem from a different angle. “With proteomics you don’t start with a list. Instead, we ask the body to tell us what is the best combination,” he says. To make this happen, the study includes participants at various stages of disease, including patients all along the spectrum, from those with no fibrosis through individuals with severe fibrosis and cirrhosis.
Blood is drawn from patients regularly, and the serum is analyzed to determine which proteins are most important in distinguishing various stages and types of disease. “You look at as many proteins as you can to see which of those proteins are actually correlated with the clinical question you’re trying to address,” Fung says. “I think this is a much stronger approach, since you don’t have to make assumptions up front; you can let biology speak to you on its own.”
Though currently involved in active investigation for identification of the markers, indications are the test will likely not be a rapid diagnostic. “I’m not sure whether a point-of-care test is the best way to go with this,” says John R. Petersen, PhD, DABCC, FACB, professor of pathology, associate director clinical chemistry, director of point-of-care testing, UTMB. “Yes, you want results relatively quickly, but in this case, I think you’d be trading speed for accuracy and reproducibility, which wouldn’t be optimal.”
Predicting the Future
Another emerging area of research lies in the promise that tests might be able to predict a specific patient’s response to therapy. For many living with HCV, treatment can impede virus-related illness. But for others, it proves a toxic combination of chemicals, and more than half the patients given this drug regimen will not respond.
NIAID’s Division of Microbiology and Infectious Diseases (DMID) estimates more than 85% of infected individuals fail to clear the virus spontaneously and develop chronic infections,4 though some believe the actual number is between 55% and 75%. Whatever the most accurate statistic, there is no denying the need for a method of assessing efficacy of treatment.
“The problem that I see in my day-to-day practice is there’s no way to predict which patients will respond to the medication,” Karyotakis says. “The next big revolution will be in the area of pharma proteomics, allowing us to stratify how individual patients might tolerate ribavirin or interferon, while identifying those who may not respond very well to the treatment.”
In addition to more-targeted treatments, there could also be considerable financial ramifications from such a test. December’s Duke University study also tracked prescription drug data, finding that spending for HCV drug therapy rose from $78 per $100,000 of new prescriptions in 1998 to $259 per $100,000 in 2000.1
“Being able to predict in advance who’s going to respond to therapy and who’s not is a very important clinical question from the patient perspective as well as from the medical side,” Fung says. “We’d like to know if we can find blood markers that can help us predict this, and there’s some data suggesting that different types of hepatitis C viral genotypes can help us do just that.”
Evaluating the Body’s Natural Response
Researchers at UTMB are also looking at the human immune system for indications of HCV-related disease. “We’re also interested in host immune response as biomarkers,” Gorenstein says. “Within hours of an infection, humans have an innate immune system that immediately responds to a pathogen invasion, setting off a whole host of immune responses.”
Gorenstein believes during this preantibody stage, the immune system creates a pattern of various cytokines, chemokines, and transcription factors that might represent a biosignature of particular pathogens. “The goal there is to be able to utilize that biosignature,” he says. “Maybe it won’t identify a specific pathogen, but it could indicate whether it’s a potentially lethal reaction, such as shock.”
The Importance of Fast Diagnosis
According to the CDC, the rate of new hepatitis C infection is on the decline, down from an average of 240,000 per year in the 1980s to approximately 30,000 per year in 2003.2 The bad news is that just as was the case 30 years ago, the majority of today’s infections result from intravenous drug use. These individuals tend to lead a highly transient lifestyle, further complicating the process of diagnosis and treatment.
“Point-of-care tests are very important at centers where there may be a population at significant risk for disease, but for whom the rate of adherence to return visits is not high,” Lee says, citing needle exchange clinics as one such example. “We are developing a rapid, point-of-care test for hepatitis C that would provide physicians and other health care professionals with a test that gives immediate results and doesn’t require any equipment to run, allowing them to test individuals who present with significant risk.”
As with virtually every illness, early diagnosis renders earlier treatment and, often, a higher success rate. “It’s important to identify individuals with HCV so they can be put on appropriate therapy as soon as possible,” Lee says. “There have been significant breakthroughs in recent years in terms of developing therapies that, in many instances, can result in clearance of the virus.”
While instant access to answers makes such a test ideal for nontraditional locations, Lee believes it will find a home in hospitals and physicians’ offices as well. “The point-of-care tests have tremendous value because they provide immediate diagnostic information for the physician.” He adds that patients will appreciate the test’s ability to aid in the diagnosis of hepatitis C using oral fluid specimens, in addition to blood samples.
Still in the design phase, the test will be patterned after the company’s existing HIV test, which provides results in approximately 20 minutes. Preclinical and clinical studies are expected to begin in late 2006.
Improved Testing, Improved Patient Care
With ever-increasing numbers of Americans dealing with HCV-related conditions, advances in testing will make life easier not only for physicians, but for patients as well.
“Ultimately, it could lead to fewer liver biopsies and both a better understanding of the history of hepatitis C and its natural course,” Snyder says. “And I think it’ll enable us to better choose those who should be treated.”
Dana Hinesly is a contributing writer for Clinical Lab Products.
References
1. Hepatitis C patients taxing medical system. Available at: [removed]http://www.healthcentral.com/newsdetail/408/529386[/removed]. Accessed February 16, 2006.
2. National Center for Infectious Disease. Viral hepatitis C fact sheet. Available at: http://www.cdc.gov/ncidod/diseases/hepatitis/c/fact.htm. Accessed February 16, 2006.
3. National Center for Infectious Disease. Viral hepatitis C. Frequently asked questions. Available at: http://www.cdc.gov/ncidod/diseases/hepatitis/c/faq.htm#1e. Accessed February 16, 2006.
4. Division of Microbiology and Infectious Diseases. What you should know about hepatitis C. Available at: http://www.niaid.nih.gov/dmid/hepatitis/hepcfacts.htm. Accessed February 16, 2006.
