A semiautomatic one-stage factor 8 assay with a commercially prepared standard.

Abstract

Abstract A one-stage factor VIII assay with a semiautomatic clot-timer and a commercial standard plasma is described. Compared to existing methods, this assay is technically simpler, more quickly performed, and less subject to human error. The 95 per cent confidence limits of individual assays, which is a superior estimate of uncertainty for parallel-line bioassays, averaged 80 to 127 per cent of the observed result even at very high or very low levels. The mean factor VIII level for 60 normal subjects was 101 per cent with a range of 58 to 200 per cent. Serial factor VIII assays in 6 normal subjects revealed wide fluctuations over the 60 day study period. This method also allows assay of factor VIII in cryoprecipitate and glycine-precipitate fractions of plasma.