A cellulose sandwich fluoroimmunoassay for Factor VIII-related antigen

We describe a cellulose sandwich fluoroimmunoassay for Factor VIII-related antigen (FVIIIR:Ag). Plasma is incubated with cellulose-antibody for 2 hours, fluorescent-labelled antiserum is added and the samples are allowed to react for an additional 2 hours. The fluorescence associated with the cellulose-antibody is measured after the tubes have been centrifuged, and the deposit washed and then digested with sodium hydroxide. Ninety-seven samples are assayed and the results are compared with radioimmunoassay (correlation coefficient 0.960) or electroimmunoassay (correlation coefficient 0.882). Between-run coefficients of variation are 8.0% to 9.9%. The cellulose-antibody reagent and the fluorescent-labelled antiserum were both stable over a period of 1 year, demonstrating a major advantage of fluoroimmunoassay over radioimmunoassay.