VIENNA (FRONTLINE MEDICAL NEWS) – Roughly half of American adults with chronic hepatitis C infection are unaware of their infection, and about one-fifth of these people with unsuspected infection likely have advanced liver fibrosis, according to a new analysis of U.S. data.

These findings “strengthen the recommendation for hepatitis C virus (HCV) screening in asymptomatic individuals,” Dr. Prowpanga Udompap said at the meeting sponsored by the European Association for the Study of the Liver.

People infected by HCV with advanced liver fibrosis have top priority for receiving curative drug treatment, according to recommendations by the American Association for the Study of the Liver and the Infectious Diseases Society of America.

People who have HCV-associated liver fibrosis that goes untreated also risk having their infection become more refractory to cure over time, they risk progressive hepatic deterioration that will eventually become symptomatic, and they face increasing risk for developing liver cancer, noted Dr. W. Ray Kim , senior author of the study and professor of medicine and chief of gastroenterology and hepatology at Stanford (Calif.) University.

Dr. Kim said he was surprised that such a large percentage of Americans who have unrecognized HCV infection also probably have substantial hepatic damage.

“To me it’s alarming that 20% of people who are not aware of their HCV infection are treatment candidates. These people are out there, but not getting treated,” he said in an interview.

Current U.S. HCV screening recommendations from the Centers for Disease Control and Prevention call for screening all Americans born during 1945-1965, “but there is no incentive to screen” and many U.S. primary care physicians don’t have HCV screening on their radar, he said.

The analysis conducted by Dr. Udompap and Dr. Kim used data collected by the National Health and Nutrition Examination Survey during 2001-2012, when the National Center for Health Statistics administered HCV testing to 45,000 of the 62,000 individuals who participated in the survey during this period.

Of the 45,000 people tested, 420 (0.9%) screened antibody positive and had infection confirmed by a second, RNA-based test. The HCV positive patients then received a survey that included a question of whether they were aware of their HCV status before their current test result notification. One hundred sixty-three people (39%) completed and returned the survey: Eighty-three said they had previously been unaware they were HCV positive, and 80 said that they had known about their infection. The 50% rate of awareness of HCV chronic infection is consistent with a previously reported rate ( Hepatology 2012;55:1652-61 ), said Dr. Udompap, a gastroenterology researcher at Stanford.

Individuals who were aware of their infection and those who were not had very similar demographic and clinical parameters. The average age was 53 years, and about two-thirds were men.

Dr. Udompap ran estimates of each respondent’s liver fibrosis and cirrhosis severity using the FIB-4 score and APRI score and data collected during the survey on age, liver enzyme levels, and platelet counts. These calculations showed that 22% of those ignorant of their HCV-positive status had a high probability of having advanced fibrosis, and 11% had a high probability of having cirrhosis, Dr. Udompap reported.

These rates tracked close to those of the people who knew about their HCV-positive status, of whom 15% had a high probability of having advanced liver fibrosis and 11% were highly likely to have cirrhosis.

Dr. Udompap reported having no financial disclosures. Dr. Kim has been a consultant to several drug companies that market, or are developing drugs, used to eradicate hepatitis C infections.

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