[HBV carriers and HDV superinfection--studies on the cases of HBsAg clearance].

We studied the annual clearance rates of hepatitis B surface antigen (HBsAg) and the annual seroconversion rates of HBsAg (HBs seroconversion rates), and the correlation between HBsAg clearance and hepatitis delta virus (HDV) superinfection in hepatitis B virus (HBV) carriers in Japan. Out of 1,029 HBV carriers followed for more than 36 months, 56 cases were cleared of HBsAg from the sera, and 24 of these cases developed hepatitis B surface antibody. The annual clearance rate of HBsAg was 0.94% and the annual HBs seroconversion rate was 0.27%. These rates increased with aging, especially above 30 years of age. Antibody to HDV was detected in three cases with increased serum alanine aminotransferase activity preceding HBsAg clearance. These data indicate that HDV superinfection may play a role in induction of the HBsAg clearance in HBV carriers in Japan.