July 9, 2001 -- The FDA has approved a new high-tech test aimed at making it easier to diagnose the virus that is the No. 1 cause of liver transplants in the U.S.
Makers of the new test say that it can pinpoint those who are most likely to develop life-threatening complications of hepatitis C. Public health experts say that hepatitis C, called HCV, infects as many as 4.4 million Americans.
The new test, which is called the AMPLICOR HCV Test, will be used to determine if there is "active HCV infection in the blood," said Michael Fried, MD, in a media teleconference Monday to announce the approval. Fried, director of clinical hepatology at the University of North Carolina, Chapel Hill, conducted some of the prelicensing studies of the new test. Roche Diagnostics in Indianapolis developed the test.
HCV is a blood-borne infection that is typically transmitted by transfusion with infected blood -- blood products weren't screened for HCV until the early 1990s -- or by the sharing of needles among injection drug abusers. The CDC estimates that HCV causes about 10,000 deaths each year but says that figure is likely to climb to 38,000 by end of this decade.
Most people who are infected with HCV have no symptoms for many years, says Fried. About 15% of people who are infected with HCV recover in about six months, but the rest develop chronic HCV infection. Among those with chronic infection, about 20% to 30% develop progressive liver disease, meaning that the disease causes cirrhosis, which can lead to liver failure and the need for a transplant. HCV is also associated with liver cancer.
One of the real difficulties in diagnosing and treating the disease is sorting out those who have been exposed but will recover from those who have chronic infection, and finally identifying those who have the greatest risk for progressive disease. The key to this sorting process, says Fried, can be found inside the cells that are exposed to the virus.
The first step is standard screening, which is done with a blood test that checks blood for the presence of HCV antibodies. "The antibody test will remain the first line screening test," says Fried.
If the screening test comes back positive, it is time to look more closely, he says. That is the stage when AMPLICOR can be useful. "We need to discover who has active infection," he says.
Active infection means that the blood has hundreds of thousands of copies of the virus, a condition called viremia, says Fried. The new test, which uses polymerase chain reaction, or PCR, technology, isolates the amount of HCV ribonucleic acid -- the genetic building blocks of the virus -- in the blood. "This test gives us a simple yes-no answer," says Fried.
Getting that answer then determines who should be given the powerful drugs used to treat HCV.
The drug therapy, a combination of interferon and ribavarin, is highly toxic and causes symptoms ranging from nausea, exhaustion and headaches to severe depression. Patients are typically put on the drug regimen for a year. Fried says that the new test can also be used to "monitor response to drug therapy."
People who have the HCV antibody but don't have active infection don't require drug therapy, says Fried.
Fried says that liver disease specialists are already using PCR technology to test for viral load in HCV patients but those tests "were not standardized and not reproducible." He says the new test is "more sensitive that other tests" and because it expresses findings in international units, or IU, "it is reproducible in any hospital or any lab."
Keith Cristie, marketing manager for Roche Diagnostics, tells WebMD that hospitals and labs will probably "bill between $100 and $150 for the test."