When HBV S-Ab is the only positive one it means you have antibody for HBV by mild infection before or by vaccination, which is good. About HBV test, there is 5 item in it: HBsAg(antigen), HBsAb(antibody),HBeAb,HBcAg,HBcAb. Different combinations of positive items have different clinical significance. If you have any kind of antigen positive, you should consult a specialist.