<prompt> Epidemiologic study of Hepatitis B is by -Hbe AgHBc AgHBs Ag is usedAnti HBc  <response>: Anti HBc appears in serum a week or two after the appearance of HBs Ag. It is earliest antibody marker seem in blood.remainlifelongg,it is an indicator of prior infection with HBV REF:MICROBIOLOGY ANANTHA NARAYANAN NINTH EDITION PAGE546 