HBsAb Rapid Screen Test Strip employs chromatographic lateral flow device. Colloidal gold conjugated surface antigen reactive to anti-HBs (sAg-Au) is coated onto a nitrocellulose membrane strip. When the sample is added, it migrates by capillary diffusion through the strip rehydrating the gold conjugate. If present, anti-HBs will bind with the gold conjugated antigens forming particles. These particles will continue to migrate along the strip until the Test Zone (T) where they are captured by HBsAg immobilized there and a visible red line appears. If there is no anti-HBs in sample, no red line will appear in the Test Zone (T). The gold conjugate will continue to migrate alone until is captured in the Control Zone (C), anti-HBs antibody and aggregating in a red line, which indicates the validity of the test.