An Assay for Antihaemophilic Factor (Factor VIII) with Some Considerations Affecting the Establishment of a Standard Reference Preparation

THE introduction of the thromboplastin generation test (Biggs and Douglas, 1953) provided a procedure for the quantitatiive assay of Factor VIII (Biggs, Eveling and Richards, 1955) based on entirely new principles. Subsequently, modified procedures have been described by many authors and among these that of Pool and Robinson (1959) presented many advantageous features. As a result of experience with this assay we have introduced modifications into the procedure and into the methods of preparing the reagents. These changes improve the accuracy of the measurements and permit a single batch of reagents to be used over a period of some months with satisfactory reproducibility of results. Making use of the modified assay, the stability of freeze-dried concentrates of human Factor VIII, stored under various con&tions, has been studied over a prolonged period. From the results obtained, recommendations for the establishment of a standard reference preparation can be formulated whch should permit the direct comparison of measurements made at widely separated times and places.

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