Evaluation of a new hepatitis B virus surface antigen rapid test with improved sensitivity.

A new rapid immunochromatographic assay based on the signal amplification system (SAS) has been developed by Diagnostics for the Real World (Europe) Ltd. for the detection of hepatitis B virus surface antigen (HBsAg) in plasma or serum specimens. The SAS format features enhanced sensitivity as a result of an increased binding valence of the detector molecules. We have now evaluated the performance of the new HBsAg rapid test (DRW-HBsAg) in comparison with a well-established commercial rapid test (Determine HBsAg; previously from Abbott Laboratories; now from Inverness Medical Innovations) and with a CE-marked enzyme immunoassay (EIA) (Hepanostika HBsAg Ultra; BioMérieux) as the gold standard. Testing of serially diluted in-house HBsAg-positive samples, the World Health Organization standard, and sensitivity and reference panels yielded an analytical sensitivity for the DRW test of 0.2 to 0.8 IU/ml across HBsAg serotypes. Evaluation with eight commercially available seroconversion panels showed that the DRW-HBsAg test detected HBsAg an average of 6.1 days (range, 3 to 8 days) earlier than the Determine assay (P = 0.0078). Test sensitivity was also examined with two low-titer HBsAg EIA-positive panels in Beijing, China. Whereas 100% of these samples were detected by the DRW-HBsAg test, only 15.0% (P < 0.0001) and 87.3% (P < 0.0001), respectively, were detected by the Determine HBsAg test. The performance of the DRW-HBsAg test was further evaluated with samples determined to be HBsAg positive or negative by the EIA in Conakry, Guinea, and Beijing, China. No significant difference in sensitivity between the DRW and Determine tests was apparent with the HBsAg EIA-reactive samples from Guinea (96.7% versus 94.4%, respectively) or China (99.46 versus 98.92%, respectively). The specificity of the Determine HBsAg test was slightly higher than that of DRW-HBsAg test (100 versus 99.2%, respectively) with samples from EIA-negative blood donors in China. In conclusion, the new DRW HBsAg rapid test is more sensitive than the Determine HBsAg test and is suitable for diagnostic and blood screening in resource-limited settings.