Factor VIII International Units and Reference Materials

Summary

The establishment of the International Standard for factor VIII has introduced a common yardstick, the international unit, which all countries can apply. This standard is a concentrate of intermediate purity, shown to be very stable on long term storage. As with all international standards it is available in limited quantities and is primarily used for the calibration of national standards used to monitor patients and in the control of therapeutic preparations.

Since 1969 in Great Britain such a national standard has been made from freeze-dried pooled plasma. This has been available in larger quantities and has been introduced into routine use in coagulation laboratories. As factor VIII in freeze-dried plasma has limited stability even when stored at —20° C, successive new batches are prepared every two years or so. The availability of a common working standard with factor VIII content specified in international units makes it possible to define diagnostic and therapeutic criteria with more precision than hitherto. This system can be applied in other countries and to other clotting factors for which an international yardstick is needed.

• References

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