Diagnosis of CHB is based on seropositivity Pirfenidone for HBsAg and persistent or recurrent elevated levels of serum alanine aminotransferase (ALT) for longer than 6 months, as defined by the criteria

of the Chinese Society of Hepatology and Chinese Society of Infectious Diseases, the Chinese Medical Association.6 In all, 1,728 CHB patients were recruited from the Department of Infectious Diseases, 3rd Affiliated Hospital, Sun Yat-sen University between May 2008 and March 2011. Those who were coinfected with hepatitis A, hepatitis C, or hepatitis E viruses were excluded. Subjects who were pregnant, were infected with human immunodeficiency virus (HIV), were alcohol or drug abusers, or had autoimmune diseases were also

excluded. All patients were unrelated and of Chinese Han ethnicity. Controls were recruited from volunteers in the same city with the same ethnicity and in the same time period. Inclusion criteria were that they were healthy subjects, as confirmed by medical examination, including normal liver enzymes, negative for HBsAg and hepatitis B eAg (HBeAg), normal MG-132 datasheet liver ultrasound and no previous hepatitis B virus (HBV) immunization, or uncertainty about vaccination history. All controls were unrelated. This gave us 1,636 control subjects (Supporting Table 1). In our association

study candidate genetic variants were first confirmed by Sanger sequencing and then examined in 500 cases versus 500 controls taken randomly from the 1,728 cases and 1,636 controls. We proceeded with analysis of the whole cohort only when P values ≤ 0.05, or odds ratios (ORs) ≥1.5 were obtained in the initial 500 cases versus 500 controls tests. Those variants not reaching the criteria were discarded. This group was comprised of 50 CHB STK38 patients and 40 controls (not included in the 1,728 cases versus 1,636 control study). Exome sequencing was performed in this group in order to identify rare sequence variants and to select candidate variants for the case-control study. In order to maximize our chance of discovering variants contributing to CHB susceptibility we attempted the “extreme phenotype comparison” approach5 in addition to the inclusion criteria mentioned above. We hypothesized that patients without identifiable common risk factors to CHB might be regarded as “susceptible” individuals. We therefore selected 50 CHB patients who had no mother-to-child transmission, blood transfusion, administration of blood products, history of unsafe injection, or HBsAg-positive sexual partner.