Hepatitis C Virus Genotype Testing Offers Cost-Effective Treatment Strategy

Patients confronted with a diagnosis of hepatitis C virus (Hepatitis C Virus) infection, along with their families, often struggle to understand a confusing array of new medical terms.

By: Mike Snyder

Patients confronted with a diagnosis of hepatitis C virus (Hepatitis C Virus) infection, along with their families, often struggle to understand a confusing array of new medical terms. What exactly does "viral load" mean? What does ALT stand for, and why does it matter? What’s the difference between fibrosis and cirrhosis?

For doctors, explaining the significance of these technical terms to distraught patients can be quite a challenge. And as research advances the scientific community’s understanding of Hepatitis C Virus, the list of terms that patients need to understand gets longer and longer.

Increasingly, the term "genotype" is making its way into these conversations. A physician’s counseling of an Hepatitis C Virus-infected patient often includes a discussion of the various genotypes of the virus, and how the patient’s genotype might affect decisions about treatment. Essentially, these genotypes reflect variations in the genetic makeup of the virus.

A Valuable Tool

Today, many liver specialists agree that determining a patient’s genotype can be a valuable tool in deciding the duration of therapy — either 24 or 48 weeks — with the current treatment of choice, a combination of the drugs interferon and ribavirin. Beyond this, however, the medical significance of genotypes remains unclear.

In a study published this year in the journal "Seminars in Liver Disease," Patrizia Farci, M.D., and Robert H. Purcell, M.D., put it this way: "Although there is consensus that the Hepatitis C Virus genotype may influence the outcome of antiviral therapy, no consensus has been reached on other important issues, such as the effects of genotype on transmission, infectivity, pathogenesis and natural history of the disease."

The growing body of research about Hepatitis C Virus genotypes stems from the intense scientific interest in the virus, which has emerged as the most common chronic blood-borne infection in the world. Hepatitis C Virus infects an estimated 4 million Americans and perhaps 170 million people worldwide. It is a major cause of chronic hepatitis, cirrhosis and liver cancer, and is the leading cause of liver transplants in the United States. At least 85 percent of those infected develop a chronic infection.

Six Genotypes Identified

Scientists have identified six major genotypes of Hepatitis C Virus, along with more than 50 subtypes. In the United States, Europe and Japan, genotypes 1, 2 and 3 are predominant. Seventy-five to 80 percent of U.S. patients are infected with genotype 1, and most of the remaining U.S. patients have genotypes 2 or 3. Unfortunately, studies show that genotype 1, which afflicts the greatest number of people in the United States, also is more resistant to therapy than genotypes 2 or 3.

According to the National Institute of Diabetes and Digestive and Kidney Disease (NIDDK), an agency of the National Institutes of Health, "Patients with genotype 2 or 3 are almost three times more likely to respond to therapy" than patients with genotype 1.

Several studies, moreover, have shown that patients with genotype 1 derive the greatest benefit from a 48-week course of treatment with interferon plus ribavirin. Patients with genotypes 2 or 3 usually do just as well with only 24 weeks of treatment.

A 1998 study published in the New England Journal of Medicine stated, "Among patients with . . . Hepatitis C Virus genotypes (other than genotype 1) who were treated with combination therapy, the response rates did not vary significantly as a function of the duration of therapy."
Such findings have prompted many physicians to order genotype testing for Hepatitis C Virus-infected patients to help determine the duration of therapy. The NIDDK specifically recommends that patients with genotype 1 receive 48 weeks of treatment while those with genotypes 2 or 3 receive 24 weeks. Because of the high costs and often-severe side effects of the drug regimen, doctors say it is foolish to continue the therapy longer than necessary to derive the maximum benefit.

Cost-Effective Approach

Emil Miskovsky, M.D., a liver specialist at the University of Texas Medical Branch in Galveston, says he routinely orders genotype testing for patients for whom therapy is being considered. "In individuals who are not interested at all in therapy or in whom therapy is not clearly indicated, genotyping may not have the same value," Miskovsky says.

The use of genotyping as a tool to guide the duration of therapy can help doctors choose the most cost-effective course of treatment, according to a 1999 study in the journal Hepatology. "The strategy using viral genotyping first and then adjusting the duration of combination therapy was the most cost-effective approach," the study states. The study compared the most accepted treatment strategies for chronic hepatitis C and considered viral eradication as the "most important endpoint." It analyzed the various alternatives based on cost, survival rates and quality of life indicators.

One of the study’s authors, Zobair M. Younossi, a liver specialist at INOVA Fairfax Hospital in Falls Church, Va., says research showing the value of genotyping in determining duration of therapy has provided considerable benefit to doctors and patients. But he cautions against making unwarranted assumptions about the meaning of the research findings. For example, he says, a patient infected with Hepatitis C Virus genotype 2 or 3 should not assume that because those genotypes are more responsive to therapy than genotype 1, they are less likely to cause serious liver disease."To say that the genotype has a role in the aggressiveness of the disease, that is less clear and may not actually be true," Dr. Younossi says.

Studies intended to determine the influence of the genotype on the severity of disease caused by an Hepatitis C Virus infection have yielded contradictory results, Drs. Farci and Purcell say in their study. "Variations in patient characteristics at the time of enrollment (in studies), especially age, duration of the infection, histological stage of the disease, and (factors such as) alcohol consumption, make it difficult to compare the results reported in the literature," they write.

Determining a patient’s genotype requires laboratory analysis of a blood sample. The test is a molecular assay that may be done in conjunction with tests to determine the presence and level of virus in the patient’s blood. Costs of the tests vary, but typically range from $250 to $375, according to John Lawson of Innogenetics, a Georgia biotechnology firm that manufactures a genotyping assay. Although the U.S. Food and Drug Administration has not approved genotype testing, many insurance carriers cover the cost of the assay, Lawson says. He advises patients to check with their insurance carrier to determine if the tests are covered.

Physicians take a variety of approaches in explaining the significance of genotypes to Hepatitis C Virus-infected patients. Dr. Miskovsky says, "I liken it to flavors of the virus, like ice cream, and explain that in the U.S. there are essentially 1, 2 and 3, but in the world there are 1 through 6. I tell them that it is relevant in terms of the length of therapy and that the test does not need to be done more than once." A patient’s genotype does not change during the course of the infection.

Future research could answer some of the many lingering questions about the medical significance of the various genotypes and subtypes of Hepatitis C Virus. In the meantime, based on persuasive evidence of its value in determining the duration of therapy, genotype testing has emerged as an important tool for patients and physicians struggling with this complex and dangerous infection.

Michael Snyder is currently an Urban Affairs reporter for the Houston Chronicle where he has worked for the past 20 years as a reporter and an assistant city editor.

In 1985, he was infected with hepatitis C through a blood transfusion administered during a surgery. Snyder’s liver disease gradually worsened, and on Feb. 4, 1998, he underwent a liver transplant at Houston’s Hermann Hospital.

He returned to work full-time at the Chronicle in June 1998. He has contributed several freelance articles to Hepatitis magazine during the past year.