Incidence rates of hepatitis C virus infection among blood donors in Japan: a nationwide retrospective cohort study.

BACKGROUND: The classification of many new cases of hepatitis virus infection as overt hepatitis does not reflect the true incidence of infection because the disease takes an asymptomatic course in some cases. In this retrospective cohort study, we aimed to estimate the incidence rates of new hepatitis C virus (HCV) infections among the blood donors.

STUDY DESIGN AND METHOD: A 5-year retrospective cohort study was conducted to estimate the incidence rates by using the medical records of the blood donors between 2008 and 2013 for HCV infection. HCV seroconversions were investigated using a chemiluminescent enzyme immunoassay and then confirmed by nucleic acid amplification tests.

RESULTS: The incidence rate of HCV infection was 0.40 per 100,000 person-years (95% confidence interval, 0.27-0.57) for HCV RNA seroconversion only and 7.32 per 100,000 person-years (95% confidence interval, 6.73-7.95) if either HCV RNA or anti-HCV seroconversion were taken into consideration. No significant difference of new HCV infections was found between the sexes.

CONCLUSION: The incidence rate of HCV infection of this study was lower than that detected in a previous 1994-2004 study in which HCV incidence was 1.86 per 100,000 person-year, which reflects the presence of an effective blood screening system and health strategies targeting hepatitis control and prevention.