Back HCV Epidemiology Undercounted Populations Raise Estimate of True U.S. Hepatitis C Prevalence

Undercounted Populations Raise Estimate of True U.S. Hepatitis C Prevalence

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The number of people living with hepatitis C virus (HCV) infection in the U.S. is probably greater than the usual estimate due to undercounting of high-risk populations in household surveys, including prisoners, homeless people, and injection drug users, researchers reported in the September 2011 issue of Liver International.

According to the most widely used estimate, about 4 million people, or 1.6% of the U.S. population, have hepatitis C. This estimate is based on data from the National Health and Nutrition Examination Survey (NHANES), which periodically collects information about health and well-being from a sample of more than 15,000 people living in American households. However, because NHANES only samples the non-institutionalized civilian population, several groups at higher risk for hepatitis C may be missed, leading to an underestimate of overall prevalence.

In the present analysis, Eric Chak from the University of California at Los Angeles and colleagues searched MEDLINE and databases from the Bureau of Justice Statistics, the Center for Medicare and Medicaid, and individual state departments of corrections looking for epidemiological studies regarding HCV in high prevalence populations. They included studies of prevalence since 1975, when the first cases of "non-A/non-B" hepatitis (the former designation of hepatitis C) were reported.

The researchers focused on groups not sampled by NHANES: incarcerated individuals, homeless people, nursing home residents, hospitalized patients, and active duty military personnel. They also included some populations with high HCV rates that are included but potentially undercounted in NHANES: healthcare workers, long-term kidney dialysis patients, injection and non-injection drug users, and veterans.

Results

  • Studies of prisoners found HCV prevalence rates ranging from 23.1% to 41.2%.
  • Studies of homeless people -- including those living in shelters and welfare hotels -- ranged from 22.2% to 52.5%.
  • 2 studies of homeless veterans reported prevalence rates of 41% and 44%.
  • The highest rates were found among homeless people with HIV, at 65% and 69.1%.
  • Hepatitis C prevalence among injection drug users varied widely -- from 27% to 93% -- with the lower rates seen among younger people and those with a shorter history of injection.
  • Prevalence among non-injecting drug users ranged from 3.9% to 31.8%, but studies did not always control for concomitant use of both injected and used non-injected drugs.
  • NHANES found an HCV prevalence of 57.5% among IDUs, which "appears to be a good estimation" of true HCV prevalence in this group.
  • Studies of veterans found HCV prevalence rates ranging from 5.5% to 10.7% -- higher than the 2.8% among veterans in NHANES.
  • A single study of active duty military personnel found a low HCV prevalence rate of 0.48% (perhaps due in part to mandatory drug testing and a low number of IDUs).
  • Overall HCV prevalence among healthcare workers (with most studies looking at emergency responders) ranged from 0.9% to 3.6%, similar to the NHANES general population rate.
  • A single study found that 4.5% of nursing home residents were HCV positive.
  • HCV prevalence among hospitalized patients ranged from 4% to 20.3%.
  • The overall prevalence of HCV among hemodialysis patients was 7.8% in the most recent national study in 2002, down from 10.4% in 1995.
  • People with hemophilia who received blood products before 1987 have very high hepatitis C prevalence -- ranging from 76.3% to 100% -- but the risk of transmission via blood or blood products has been "nearly eliminated" since the advent of accurate screening in 1992.
  • The most conservative estimates indicate that there are at least 372,754 incarcerated people, 142,761 homeless people, and 6805 active duty military personnel uncounted in NHANES.
  • The most conservative estimate suggests that 5.2 million people overall are living with hepatitis C in the U.S. today (range 5.2 to 7.1 million).
  • Approximately 1.9 million of these individuals were unaccounted for in the latest NHANES survey (range 1.9 to 3.8 million).

"Our results indicate that [HCV] infection may be more prevalent than previously thought and underscores the importance of more comprehensive sampling among persons at a high risk for chronic HCV infection," the researchers summarized.

Along with recent projections of an dramatic increases in HCV-related complications over the next 20 years, these findings "highlight the burden of HCV infection especially in high-risk populations and underscore the importance of education and prevention programs targeting these persons before they become infected or before long-term complications develop if already infected," the authors elaborated in their discussion.

Perhaps the greatest contributor to recent decreases in HCV prevalence among injection drug users -- the largest at-risk group -- is outreach and harm reduction programs, they added, concluding, "Our findings underscore the importance of the interventions necessary to decrease new infections in high-risk groups."

Investigator affiliations: Department of Medicine, UCLA-Olive View Medical Center, University of California at Los Angeles, Sylmar, CA; Division of Gastroenterology and Hepatology and Center for the Study of Hepatitis C, Department of Medicine, Weill Cornell Medical College, Cornell University, New York, NY; Department of Medicine, University of Cincinnati College of Medicine, Cincinnati, OH; Department of Medicine, University of Miami School of Medicine, Miami, FL; Department of Medicine and Surgery, David Geffen School of Medicine, University of California at Los Angeles, Los Angeles, CA.

9/23/11

Reference

E Chak, AH Talal, KE Sherman, et al. Hepatitis C virus infection in USA: an estimate of true prevalence. Liver International31(8): 1090-1101 (abstract). September 2011.