Since the discovery of occult hbv, that is HBsAg -ve but detectable hbvdna, blood
donation services are more cautious if a donor is HBcAb positive, indicating a past hbv infection
and therefore may potentially have occult hbv. The more advanced donation services will now screen donors using a nucleic acid test.
Since we know many people have been exposed and recovered from HBV, a blanket rejection of everyone with positive HBcAb will significantly reduce the donor pool.