Published: Mar 3, 2014
By Michael Smith, North American Correspondent, MedPage Today
About 2.7 million people in the U.S., roughly 1.0% of the population, have chronic hepatitis C (HCV), according to new CDC prevalence estimates for the period from 2003 through 2010.
That appears to be down from the previous estimate of 3.2 million for the period 1999 through 2002, or about 1.3% of the population, according to Scott Holmberg, MD, and colleagues at the agency.
But the 95% confidence intervals of the estimates overlap, so that the prevalence might not have changed significantly, the researchers cautioned in the March 4 issue of Annals of Internal Medicine.
On the other hand, Holmberg and colleagues noted, the figure of 1.0% is likely an under-estimate because the data -- from the regular National Health and Nutrition Examination Surveys (NHANES) -- do not include the homeless and those behind bars.
Those groups, the researchers said, are "probably at higher risk for HCV infection."
The report comes as the annual Conference on Retroviruses and Opportunistic Infections opens in Boston, where data are expected on new therapies for HCV.
The NHANES is a nationally representative household survey of about 5,000 participants a year that includes interviews, physical exams, and testing of biological samples, including blood.
For the 2003-2010 and 1999-2003 analyses, investigators tested serum samples from participants 6 and older for antibody to HCV, an indication of current or previous infection. If the samples were positive or indeterminate, they were tested for HCV RNA, which indicates current chronic infection.
Of the 30,074 participants analyzed, 273 tested positive for HCV RNA; extrapolating that to the general population suggested a prevalence of 1.0% or 2.7 million people, Holmberg and colleagues reported.
Breaking the analysis down by age suggested that an estimated 2.68 million of those chronically infected were 20 or older, the researchers reported, and most of them were so-called baby boomers -- born between 1945 and 1965.
In that age group, the estimated prevalence of chronic HCV infection was 2.6%, corresponding to 2.16 million people, Holmberg and colleagues reported.
Put another way, they noted, the prevalence among those born between 1945 and 1965 is six times greater than that among other adults, and represents 81% of all those chronically infected with HCV, they estimated.
Analysis of demographic factors suggested that, compared with people who had never been infected with HCV, those who had ever been infected were more likely to be 40 to 59, male, and non-Hispanic black.
They were also more likely to have a high school education or less and to have a lower family income.
The analysis also showed that illicit drug use (including injection drugs) and receipt of a blood transfusion before 1992 were significantly associated with chronic HCV infection.
But, Holmberg and colleagues noted, 49% of people with HCV infection did not report either risk factor, suggesting that risk-based screening is likely to miss a large proportion of people with the virus.
To such screening, the CDC has recommended adding a one-time HCV test for all baby boomers, hoping to identify some 800,000 people currently not aware of their infection.
Primary source: Annals of Internal Medicine
Source reference: Denniston M, et al "Chronic hepatitis C virus infection in the United States, National and Nutrition Examination Survey 2003 to 2010" Ann Intern Med 2014; 160(5).