My Hbsag Screening Showed Reactive However When They Tested My

My hbsag screening showed reactive however when they tested my hbsag quantitative it showed non reactive because i only got 0.37 COI which is normal. How come i have abnormal results? I have no symptoms of hep b and my anti hep b is reactive because i had a booster last 2014. My hep b titer showed from 12 it became 0000 after the booster shot. Could this be the cause of such abnormal result?