RESUMO
BACKGROUND: Currently used techniques for quantitation of HBsAg often yield discordant results; therefore, development of quantitation techniques that can detect HBsAg with high accuracy has become very important. Recent advances have led to the development of several HBsAg detection systems. Here, we evaluated the performance of 3 newly developed detection systems, which can detect HBsAg both qualitatively and quantitavely, and determined the concordance among their results. METHODS: Four hundred and thirty two samples assigned to 4 groups-patient group, dilution group, weakly reactive group, and linearity group- were subjected to qualitative and quantitative detection of HBsAg by using the 3 systems developed by 3 major manufacturers; Abbott Architect, Roche E170 and Siemens Centaur XP. RESULTS: The results for the qualitative analyses were closely concordant among the three systems (98.3%) for all 432 samples. In 123 samples that were determined as HBsAg-negative, E170 (76%) distributed frequently at the upper half level (0.5-1.0) of negative reference range, compared with Architect (11%) and Centaur XP (22%). In particular, in 65 samples that were diluted from the strongly positive samples to obtain weakly positive samples, the average index values obtained using Architect (3.6 S/CO), E170 (4.2 COI) and Centaur XP (11.4 index value) differed significantly (P<0.0001). In the antiviral treatment group and the post-liver transplantation group, no inconsistency was observed among the results of the qualitative and quantitative assays. In the 18-fold serially diluted samples, no linearity was observed. CONCLUSIONS: Because of the possibility of false-positive detection in the HBsAg-negative samples, regular management of equipment and appropriate selection of reagents are very important. In weakly positive samples, quantitative assay has not to be replaced for qualitative assay. Therefore, the qualitative assays should be used for screening the samples, whereas the quantitative assays should be used for monitoring the Hepatitis B virus (HBV) load in the samples determined as HBsAg-positive. The qualitative index value should not be interpreted as a quantitative measure of HBV load.