HCV population undercounted by 1 million

January 2006

The number of people in the United States who have been infected with the hepatitis C virus (HCV) is underestimated by approximately 1 million, according to a study presented at the 56th Annual Meeting of the American Association for the Study of Liver Disease.

The undercount means that estimates of serious liver disease and the corresponding need for transplantation are worse than currently thought, said Brian Edlin, MD, associate professor of medicine and public health at the Weill Medical College of Cornell University in New York.

The federal government used blood samples from the National Health and Nutrition Examination Survey (NHANES), which does not consider several high-risk HCV populations, including the incarcerated, homeless, hospitalized, residents of nursing homes and active military, to calculate its previous estimates of HCV prevalence.

“NHANES is essentially a survey of the housed, civilian, noninstitutionalize population,” explained Edlin.

A more accurate count of people who have been infected with HCV is about 5 million compared with the currently estimated 3.9 million.

A current undercount of people infected with HCV has very important implications for health care costs and infrastructure needs, he said.

Infrastructure implications

“The undercounted groups are much less likely to have access to adequate health care and treatment for hepatitis C than other [people], so the estimates of the number of cases of serious liver disease in the coming years — and the shortage of livers for transplantation — will be much worse than currently estimated,” said Edlin.

Edlin and colleagues arrived at the numbers by combining NHANES data with data from the U.S. Census Bureau, the Centers for Medicare and Medicaid Services, the U.S. Bureau of Justice and published medical literature.

The two largest groups that the NHANES survey does not count are the incarcerated and homeless, said Edlin. In the United States, the estimated HCV prevalence rate for the 1.9 million people who are incarcerated is 31.7%, which translates to an additional 618,000 people with HCV. The estimated prevalence is 34.5% for the unaccounted 840,000 homeless, which equals an additional 290,000 people with the infection. The estimated prevalence among people who are hospitalized (16.9%), nursing home residents (4.5%) and active military (.45%) adds another 110,000, 73,000 and 6,600 people with HCV, respectively.

The study may be underestimating the number of people with HCV by another half million to 1 million. “Several studies have suggested that [people] in temporary or unstable housing may outnumber those who are literally homeless on any given night by three- to fourfold,” said Edlin.

He admitted that the study’s estimates are “certainly less precise than the NHANES estimate.” However, “they are likely to be more accurate.”

Surveillance systems need to recruit representative samples of socially marginalized populations to be more accurate, according to Edlin.

Including these populations in surveillance would also help bring to light the need for treatment.

Edlin noted that less than 1% of the prison population is likely being treated, despite a prevalence of 30% to 40%. “The lack of treatment is completely unjustified. For instance, in some states, cirrhosis is not even an indicator for treatment,” he said.

For more information:

• Edlin B. Abstract 44. Presented at: 56th Annual Meeting of the American Association for the Study of Liver Disease; Nov. 11-15, 2005; San Francisco.