Coexistence of hbsag and anti hbs?

It's possible.: When HBsAg and HBsAb are detected simultaneously, the first thing to do is to recheck the labs to be sure it is not in error. If it is confirmed, it is a rare instance of a mutation in the HBsAg region, and there is not good data about the response to conventional therapies. Be sure you were seeing an experienced hepatologist if this is present. Good luck.