Measurement of factor VIIIRAg-1. A method for use in the Hyland laser nephelometer

Factor VIIIRAg was measured by laser nephelometry using a new diluent containing a citrate-carbonate buffer, pluronic polyol P94 and triton X100. No pre-treatment of the samples was required, the incubation time was 0.5 to 1.5 hours depending on the antiserum used, and the tests could be read during the following 4 hours (plasma) or 1.5 hours (intermediate purity F VIII). The CV for the assay was less than 10% for plasma or dilutions of plasma in which the minimum detectable amount of factor VIIIRAg was about 0.04 u/ml. A significant correlation was obtained between the nephelometric method and the Laurell rocket method using plasma, but agreement between the methods when therapeutic products were assayed was poor.