Among people with hepatitis C, the risk of serious liver disease is much higher in those who also have HIV than in those without the AIDS-causing virus, a new study finds.

This is true even among patients with HIV who are otherwise benefiting from antiretroviral therapy to treat the virus, the University of Pennsylvania researchers said.

They analyzed data from more than 4,200 patients with both hepatitis C and HIV who were receiving antiretroviral therapy. In addition, they looked at data on more than 6,000 patients with hepatitis C only. The patients received care between 1997 and 2010.

The HIV/hepatitis C patients had an 80 percent higher rate of serious liver disease than those with hepatitis C only, according to the study, which was published in the March 18 issue of the journal Annals of Internal Medicine.

Even HIV/hepatitis C patients who had a good response to antiretroviral therapy for HIV still had a 60 percent higher rate of serious liver disease than those with hepatitis C alone.

Serious liver diseases were higher among HIV/hepatitis C patients with advanced liver fibrosis, diabetes and severe anemia, and among those who weren’t black, the study also found.

About 20 percent to 30 percent of HIV patients also have hepatitis C, likely due to shared causes of infection.