Detection of hepatitis B surface antigen in whole blood by coupled particle light scattering (Copalis).

Coupled particle light scattering (Copalis) is a homogeneous immunoassay technology that permits simultaneous determination of multiple analytes in serum, plasma, or whole blood. Copalis differentiates monomeric latex microparticles from latex aggregates and cells on the basis of their unique light scatter properties. Copalis readily discriminates small (approximately 0.1 micron) differences in latex microparticle size. Therefore, multiple simultaneous assays are configured by the use of mixtures of different-size latex microparticles. The Copalis research immunoassay for hepatitis B surface antigen (HBsAg) is configured in a sandwich format where the extent of light scatter histogram broadening due to HBsAg-mediated binding of colloidal gold to latex provides the basis for antigen quantification. Simultaneous Copalis forward- and wide-angle light scatter measurements allow discrimination of latex microparticles from the cell components of whole blood. Consequently, direct detection of HBsAg in unprocessed whole-blood samples by Copalis is feasible.