Table 1.

Inclusion and exclusion criteria.

Inclusion criteria

Cases (DP,chronic HBV infection)

1. HBsAg, anti-HBc positive for at least 6 months and no history of hepatitis B vaccination

2. anti-HAV, anti-HEV, HDAg negative and/or anti-HDV negative

3. Anti-HCV negative, HCV RNA negative

4. For DP cases in the first stage, anti-HBs positive for at least 6 months; for chronic HBV infection cases in the second stage, anti-HBs can be positive or negative

Controls (SP, HBV clearance)

1. Anti-HBs and anti-HBc positive or anti-HBs positive and no history of hepatitis B vaccination; HBsAg negative

2. HBV-DNA negative, anti-HAV, anti-HEV, HDAg negative and/or anti-HDV negative

3. Anti-HCV negative, HCV RNA negative

Exclusion criteria*

1. Evidence of past or current infection by HCV or HDV

2. With other hepatitis virus infection

3. Other systemic disease not related to HBV infection

4. Age less than 18 for all cases and controls

5. Not of Han ethnicity

DP Double positive; SP single positive.

*Excluded from enrollment if one or more of the exclusion criteria were met, applicable for all the two stage samples.