The sensitive detection and quantitation of antibody to HCV by using a microsphere-based immunoassay and flow cytometry.

Antibody to HCV core and NS3 was quantified by using a microsphere immunoassay and flow cytometry. Antibody to core and NS3 was elevated in the 85 seropositive blood donors tested. The amount of either antibody varied over two logs although greater variation was seen with the antibody to NS3 than was seen with antibody to core. In three documented acute HCV cases, the microsphere assay detected antibody prior to antibody detection using the reference methods. Twenty donor samples were indeterminate by the reference methods: 45% of these were indeterminate with the microsphere assay while 25% were negative and 30% were positive. As compared to enzyme immunoassay the microsphere assay showed a 5-fold increase in sensitivity. The microsphere assay demonstrated increased sensitivity for the quantification of specific antibody to HCV core and NS3 and was useful in resolving a significant proportion of indeterminate samples.