Trends in the prevalence of thrombocytopenia among individuals iInfected with hepatitis C Virus in the United States, 1999-2008

BACKGROUND: Thrombocytopenia is associated with the natural history of hepatitis C virus (HCV) infection and anti-viral therapy. Recent, national estimates of the clinical burden of thrombocytopenia among HCV-infected individuals in the United States are unavailable. Bi-yearly data from the 1999-2000 to 2007-2008 National Health and Nutrition Examination Surveys (NHANES) were used to examine the prevalence of thrombocytopenia among HCV-infected individuals in the United States. RESULTS: Among 467 HCV-infected individuals in the survey (weighted population = 3,597,039), mean weighted age was 46.7 years (standard deviation = 15.5) and 61.7% were male. Overall, 7.6% met the study definition of TCP at the 150 × 10(9)/L threshold; 4.5%, 2.0%, and 0.8% had platelet counts below 125, 100, and 75 × 10(9)/L, respectively. The 2-year weighted prevalences of thrombocytopenia (150 × 10(9)/L threshold) from 1999-2008 were 4.9%, 8.6%, 6.5%, 4.1%, and 12.9%. The unadjusted biannual time trend (odds ratio) was 1.16 (95% confidence interval = 0.82-1.64). In the two adjusted models, the odds by time ranged from 1.24-1.40, depending on whether the model included demographic or laboratory variables or both, but did not reach statistical significance. Age was positively and significantly related to thrombocytopenia status. CONCLUSIONS: As the HCV-infected population ages, the prevalence of thrombocytopenia is expected to rise. This study provides limited evidence of such an effect at the national level.