Hello, the presence of HBsAg means that an individual has come into contact with hepatitis B virus. There are some rare exceptions to this rule. If the core antibody (anti-HBc) is negative then there are two possibilities. (1) there is an infection that has not yet led to increased antibodies against core antigens (2) there is no infection and HBsAg is reactive because of other antigens that cause cross-reactivity. The second is the most likely scenario unless your daughter had symptoms as well. In any case a repeat and more complete testing for hepatitis is warranted. So, besides HBsAg and anti-HBc, also please include the tests: - HBeAg - antiHBe - anti-HBs - liver function tests Doing them in a couple of weeks would be appropriate unless she has symptoms. If she does, then she ll need to contact an infectious diseases or hepatology specialist to receive treatment. I hope I ve helped! If you d like more information, you can contact me again. Kind Regards!