Performance Utility of High Sensitivity Quantitative Assay for HBs Antigen

: A high sensitivity quantitative assay for hepatitis B virus (HBV) surface antigen (HBsAg-HQ assay) was recently developed and is useful for earlier detection of HBV reactivation. We created HBsAg-HQ assay operational proce- dures by the sample transport system and laboratory information system. In this study, we evaluated the perfor- mance and utility of the HBsAg-HQ assay based on our operational procedures using internal quality control (IQC) data and 13,762 samples routinely measured for 8 months. The IQC data of the HBsAg-HQ assay demonstrated good accuracy (CV: 1.6-2.7%). The difference in IQC data between two of the same analyzers or several reagent lots had no clinical significance. Of 13,762 samples, HBsAg titer was negative in 12,592(91.5%) and positive in 1,169(8.5%), and HBsAg negative samples were remarkably lower(<0.001 IU/mL) than the cut-off value(0.005 IU/mL). Among 114 HBsAg weakly positive samples ranging from 0.005 to 1.000 IU/mL, false positive results occurred in 12 samples, which were converted into negative results after re-measurement. We could effectively perform carry-over prevention and dilution of high titer samples using our operational procedures. Furthermore, we performed inhibition test in 52 HBsAg weakly positive samples, and 20 samples, most of which were taken from patients with connective tissue disease or malignancy, were judged as non-specific reactivity. Taken together, our operational HBsAg-HQ assay procedures may contribute to efficient workflow for routine testing. Moreover, the HBsAg-HQ assay may be clinically useful for not only highly sensitive assays, but also for reducing false positives.