First, other risk factors, such as, an advanced age and histologic disease status, can confuse attempts to determine whether EtOH RBV dose reduction is responsible (8). Second, RBV dose reduction is the only mechanism whereby ITPA variants might associated with virological response (11). Third, RBV dose reduction may not be associated with virological response if RBV is not discontinued (25, 26). This study has limitations that should be mentioned. First, it is limited by its retrospective, single center design. Second, it was conducted in a Korean population, and thus, the results obtained may not be applicable to other ethnicities. In conclusion, there are strong points in our study. First, ITPA genotype distributions in Koreans and Caucasians differ.

Second, non-CC at rs1127354 (regardless of rs7270101 genotype) is strongly associated with protection from RBV induced anemia. Third, RBV dose reduction due to RBV induced anemia is influenced by ITPA variants, and finally, ITPA genotype is not associated with virological response. Footnotes This research was supported by Gachon University Gil Medical Center research fund (2011). The authors declare that they have no proprietary, commercial, or financial interests that could be construed to have inappropriately influenced this study.
Hepatitis B virus (HBV) is the leading cause of acute hepatitis, chronic hepatitis, cirrhosis, and hepatocellular carcinoma (HCC) in South East Asia, China, and sub-Saharan Africa [1]. The prevalence of HBV infection in these regions ranges from 5% to 20% [2].

Seropositivity for hepatitis B surface antigen (HBsAg) was estimated at 8% to 9% in males and 5% to 6% in females in the 1980s [3]. The introduction of hepatitis B vaccination has dramatically decreased acute and neonatal HBV infection in many countries. In Korea, universal vaccination of all infants has been performed since 1991 and nationwide strategies have been implemented since 1995 [4]. Prior to the introduction of the vaccination program, approximately 8% of the general Korean population was HBsAg-positive [5]. Following the introduction of HBV vaccination, HBsAg prevalence rates have decreased, from 10% in the 1980s to 3.8% in 2007 in the general population [6]. This rate decreased further, to 0.4% in teenagers and 0.2% in children younger than 10 years [7]. Korea is now classified as an intermediate HBV endemic area (2% to 7% prevalence) [6].

Although the prevalence of HBV has decreased, few epidemiological studies have investigated changes in HBV infection rates and the related demographic or environmental factors. Some Korean studies have been conducted using nonrepresentative or small samples from selected communities. Since 1998, a nationwide survey, named The Korea National Brefeldin_A Health and Nutrition Examination Survey (KNHANES), has been conducted.