African American adults with chronic hepatitis C virus (HCV) infection are less likely to respond to standard combination therapy with peginterferon and ribavirin, a study confirms.

In a statement, study author Dr. Charles D. Howell of the University of Maryland in Baltimore said the reduced response rate among African American patients is not caused by “the usual predictors,” such as patient age, gender, HCV levels prior to treatment, amount of fibrosis in the liver biopsy nor amount of medication taken.

In a multicenter treatment trial, 196 African American and 205 Caucasian American patients with HCV infection and similar baseline characteristics received standard treatment consisting of peginterferon alfa-2a (180 micrograms/week) and ribavirin (1000 to1200 mg/day) for up to 48 weeks.

The response rate was 28 percent in African Americans compared with 52 percent in Caucasian Americans, a significant difference.

Racial differences in viral responses were evident as early as 4 weeks after the start of treatment, the team notes. “Breakthrough viremia” occurred more frequently in African Americans than Caucasian Americans (13 percent vs. 6 percent), but relapse rates were comparable (32 percent vs. 25 percent).

The proportion of the total maximum dose of peginterferon and ribavirin taken was lower among African Americans than Caucasian Americans. However, in multivariate analysis, this did not account for the racial difference in response rates.

The basis for the racial difference in response rates is being addressed by ongoing supplementary studies.

It’s estimated that 1.3 percent of the US population, approximately 3.2 million Americans, have chronic HCV infection. HCV is now the leading cause of chronic liver disease and the most common indication for liver transplantation in the US.

SOURCE: Gastroenterology August 2006.