Lyophilized Plasma as an Assay Standard for Factor VIII: Calibration and Control with Fresh Plasma Samples

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Abstract
Samples of fresh human citrated plasma were lyophilized, mixed and stored in batches at 4°C under vacuum. This material, reconstituted with water, was examined as a standard for factor‐VIII assays. Its initial potency was about 30% of average normal plasma and it lost potency at the rate of 2.6% per month at 4°C and 16.3% per month at room temperature. It is therefore not suitable as a factor‐VIII standard.The experimental error of the assay was estimated as 83‐120% of the mean. This interval includes approximately 90% of estimated potency ratios whose true values are 100%. The results confirmed that the factor‐VIII concentration in a single individual is reasonably constant and that the range of concentrations in a group of normals is approximately 50‐200% of the mean. The distribution of the values was approximately log‐normal. It is suggested that, in the absence of a more satisfactory stored standard, a single subject who has been calibrated against a population of normals could serve as a factor‐VIII standard.