Hepatitis B and C virus infection among 1.2 million persons with access to care: factors associated with testing and infection prevalence

Abstract

Background: Little is known about viral hepatitis testing and infection prevalence among persons in private healthcare organizations (HCOs) in the United States.

Methods: To determine the frequency of and characteristics associated with viral hepatitis testing and infection prevalence among adults with access to care, we conducted an observational cohort study among 1.25 million adults from 4 US HCOs and included persons with ≥1 clinical encounter during 2006-2008 and ≥12 months of continuous follow-up before 2009. We compared the number of infections identified with the number expected based on adjusted data from the National Health and Nutrition Examination Survey (NHANES).

Results: Of 866,886 persons without a previous hepatitis B virus (HBV) diagnosis, 18.8% were tested for HBV infection, of whom 1.4% tested positive; among 865,659 without a previous hepatitis C virus (HCV) diagnosis, 12.7% were tested, of whom 5.5% tested positive. Less than half of those with ≥2 abnormal alanine aminotransferase (ALT) levels were subsequently tested for HBV or HCV. When tested, Asians (adjusted odds ratio [aOR] 6.33 relative to whites) were most likely HBV infected, whereas those aged 50-59 years were most likely HCV infected (aOR 6.04, relative to age <30 years). Based on estimates from NHANES, nearly one-half of HCV and one-fifth of HBV infections in this population were not identified.

Conclusions: Even in this population with access to care and lengthy follow-up, only a fraction of expected viral hepatitis infections were identified. Abnormal ALT levels often but not consistently triggered testing. These findings have implications for the identification and care of 4-5 million US residents with HBV and HCV infection.

Figure 1.

Estimated proportion of unidentified hepatitis B virus (HBV) infections among persons enrolled during 2006–2008 in 4 US healthcare organizations. Race-specific HBV surface antigen (HBsAg) prevalence from the National Health and Nutrition Examination Survey (NHANES) was used to estimate the number of expected HBV infections. Limiting analysis to the 71% of persons with known race, the total number identified with HBV infection was the sum of the number found through testing (1604 incident infections) and the number initially excluded from the testing frequency analysis due to a hepatitis B diagnosis code (700 prevalent infections), or approximately 2304 infections. Using NHANES race-specific estimates (where HBsAg prevalence for NHANES “other” race* corresponds to Asians, Native Hawaiian/Pacific Islanders, and American Indian/Alaska Natives in our cohort), approximately 2920 persons would be expected to test positive for HBsAg. Therefore, 616 (21.1%) of 2920 expected HBV infections in our cohort were unidentified. Abbreviations: HBsAg, hepatitis B surface antigen; HBV, hepatitis B virus; HCOs, healthcare organizations; ICD-9, International Classification of Diseases, Ninth Revision; NHANES, National Health and Nutrition Examination Survey.

Figure 2.

Estimated proportion of unidentified hepatitis C virus (HCV) infections among 867 589 adults enrolled during 2006–2008 in 4 US healthcare organizations. Age-specific anti-HCV prevalence from the National Health and Nutrition Examination Survey (NHANES) was used to estimate the number of expected HCV infections. The total number of persons identified with HCV infection was the sum of the number identified through testing (6008) and the number initially excluded from the testing frequency analysis due to a hepatitis C diagnosis code (1930), or approximately 7938 infections. Using age-specific NHANES estimates of HCV infection prevalence, the total number of persons predicted to test positive for anti-HCV in the cohort was approximately 13 963. Therefore, approximately 6025 (43.1%) of 13 963 HCV infections were unidentified. Abbreviations: Anti-HCV, IgG antibody to hepatitis C virus; HCO, healthcare organizations; HCV, hepatitis C virus; ICD-9, International Classification of Diseases, Ninth Revision; NHANES, National Health and Nutrition Examination Survey.