Abstract
PURPOSE: Few population-based studies have estimated the number of persons diagnosed with chronic hepatitis B (CHB) infection in the United States. Our objective was to estimate the prevalence of diagnosed CHB infection among persons enrolled in the U.S. Medicaid programs of California, Florida, New York, Ohio, and Pennsylvania between 2000 and 2007. As part of our analyses, we confirmed the accuracy of CHB diagnoses within the Medicaid database. METHODS: CHB infection was defined by the presence of two outpatients CHB diagnoses recorded more than 6 months apart. Two clinicians reviewed the medical records of a random sample of patients who met this definition to confirm the diagnosis, which enabled calculation of the positive predictive value (PPV). The period prevalence of diagnosed CHB infection among Medicaid enrollees with at least 6 months of membership from 2000 to 2007 was then estimated, adjusting for both the PPV and estimated sensitivity of our definition of CHB infection. RESULTS: The definition of CHB infection accurately identified clinician-confirmed cases (PPV, 96.3%; 95% confidence interval [CI], 87.3-99.5). Using this definition, 31,046 cases of CHB were diagnosed among 31,358,010 eligible Medicaid members from the five states (prevalence, 9.9 [95% CI, 9.8-10.0] per 10,000). Adjusting for the PPV and estimated sensitivity of our CHB definition, the prevalence of diagnosed CHB infection was 15.6 (95% CI, 15.4-15.7) per 10,000. CONCLUSIONS: Two outpatient CHB diagnoses recorded more than 6 months apart validly identified clinician-confirmed CHB. The prevalence of diagnosed CHB infection among U.S. Medicaid enrollees was 15.6 per 10,000.