(Hepatology) -- Chronic liver disease (CLD) is the 10th most common cause of death in the United States and viral hepatitis is one of its important causes. However, traditional methods of coding deaths due to CLD do not include viral hepatitis, leading some to believe that the number of hepatitis-related deaths have been underestimated.

A new study, published in the February 2004 issue of Hepatology, sought to better determine death rates from chronic liver disease, including those due to viral hepatitis. It found that death rates for CLD related to hepatitis C increased by 220 percent between 1990 and 1998, even as CLD death rates declined overall.

Hepatology is published on behalf of the American Association for the Study of Liver Diseases (AASLD) by John Wiley & Sons, Inc.

Traditional methods used to calculate CLD mortality use death certificate data that are based on International Classification of Disease codes. There is no CLD code for viral hepatitis, even though population-based studies have shown that the virus is a common cause of CLD.

To better quantify the role of viral hepatitis in CLD deaths, researchers, led by Sirenda Vong of the National Center for Infectious Diseases, reexamined death certificate data for CLD deaths, as well as deaths related to viral hepatitis and other relevant sequelae of CLD. They analyzed this information, along with corresponding demographic data, to describe rates and trends in CLD mortality in the United States from 1990 to 1998.

They found that age-adjusted death rates for CLD decreased 4.5 percent from 1990 to 1998, however for CLD related to hepatitis C, death rates increased by 220 percent. "Decreases in CLD deaths not related to viral hepatitis were counterbalanced by an increase in deaths from CLD caused by chronic hepatitis C," they report. They suggested that the large increases in HCV-related mortality were related to improved awareness and testing for the viral infection among patients with chronic liver disease.

Under the expanded definition of death from CLD, the number of 1998 CLD deaths increased by nearly 23 percent and the proportion of CLD deaths due to viral hepatitis increased by 19 percent.

"The decline in CLD mortality observed during the previous decades and sustained through the early 1990s did not continue after 1994, largely because of increased in HCV- related deaths," the authors report.

The researchers also considered demographic data and found that American Indian and Alaskan native populations suffered disproportionately from chronic liver disease. Death rates for these groups were more than twice those of other racial groups, and increased as the 90s progressed. These disparities demonstrate the need for social and public health interventions that target high-risk populations, the authors suggest.

"Future analyses of CLD mortality and its causes should include viral hepatitis and sequelae of CLD deaths because of the narrow definition of CLD in ICD," the authors conclude, adding, "further studies are needed to evaluate the validity of estimates of the mortality burden from CLD generated from national mortality data and to characterize better the causes of CLD deaths."