By Michael Smith, North American Correspondent, MedPage Today
Published: November 06, 2011
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco
SAN FRANCISCO -- African Americans face a "triple whammy" when it comes to the hepatitis C virus, a researcher said here.
Two aspects of this triple threat are well known: the high prevalence of the virus in the African-American community and the lower response to therapy of infected individuals, according to Zobair Younossi, MD, of Inova Fairfax Hospital in Fairfax, Va.
But there's a third threat: African Americans don't spontaneously clear the virus as often as other racial and ethnic groups, Younossi reported at the annual meeting of the American Association for the Study of Liver Diseases.
"I would call it a triple whammy -- high prevalence, lower chance of spontaneous clearance, and then the lower chance of sustained virologic response," Younossi told MedPage Today.
"This is the population that we really need to focus on and develop something that will help," he said during a poster presentation.
Younossi and colleagues analyzed data collected from 2005 to 2008 by the National Health and Nutrition Examination Survey (NHANES), which included clinical and laboratory data on nearly 15,000 participants.
Included in the data were results for tests for hepatitis C antibodies and RNA, Younossi said, which allowed the researchers to look at rates of spontaneous clearance of the virus.
All told, they found that 192 of the 14,750 participants had antibodies to the virus. Also, 149 of the participants had hepatitis C RNA, indicating they remained infected. The other 43 had cleared the virus naturally.
In a univariate analysis, the only factor that was significantly different between the groups was the proportion of African Americans who remained infected versus those who had cleared the virus (P=0.0163), Younossi said.
The rate of clearance among African Americans in the cohort was 9.25%, compared with 27.2% among Caucasians and 31.2% among Hispanics.
In a multivariate analysis, Younossi said, the only independent predictor of not being able to clear the virus was African-American race. The odds ratio for non-clearance for African Americans, compared with Caucasians, was 3.80, with a 95% confidence interval from 1.31 to 11.36, which was significant at P=0.015.
The finding is, "not unexpected," according to Gary Davis, MD, of Baylor College of Medicine in Houston, who was not involved in the study.
Davis told MedPage Today that analysis of smaller cohorts had suggested the disparity and the confirmation in such a large group is useful and important.
The explanation may lie in a genetic factor: a single nucleotide polymorphism in the IL28b gene that has been shown to reduce the response to therapy, and may also cut the rate of spontaneous clearance, he added.
People with the two copies of the C allele of the gene respond best to treatment, while those with two copies of the T allele are most resistant. Those with one copy of each allele fall in the middle.
There is evidence that the same is true for the ability to clear the virus naturally, Davis said, and since the T allele is more common in African Americans, it would explain the findings of Younossi and colleagues.
Younossi told MedPage Today it's likely that the genetics plays an important role, but he said he believes that genetics is only a component and not the main reason for the response rates.
The researchers did not report external support for the study. Younossi reported financial links with Vertex, Biolex, Tibotec, and Salix.
Davis reported financial links with Vertex, Tibotec, Genentech, Abbott, Boehringer Ingelheim, Bristol-Myers Squibb, Gilead, Novartis, and Pharmasset.
Primary source: Hepatology
Source reference:
Younossi ZM, et al "African Americans are less likely to have natural clearance of hepatitis C virus (HCV) infection: the findings from recent U.S. population data" Hepatology 2011; 54(4); Abstract 396.
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