Standardization of Factor VIII – IV. Establishment of the 3rd International Standard for Factor VIII: C Concentrate

Summary

An international collaborative study was carried out to establish a replacement for the current (2nd) international standard for Factor VIII: C, concentrate. Twenty-six laboratories took part, of which 17 performed one-stage assays, three performed two-stage assays and six used both methods. The proposed new standard, an intermediate purity concentrate, was assayed against the current standard, against a high-purity concentrate and against an International Reference Plasma, coded 80/511, previously calibrated against fresh normal plasma.

Assays of the proposed new standard against the current standard gave a mean potency of 3.89 iu/ampoule, with good agreement between laboratories and between one-stage and two- stage assays. There was also no difference between assay methods in the comparison of high-purity and intermediate purity concentrates. In the comparison of the proposed standard with the plasma reference preparation, the overall mean potency was 4.03 iu/ampoule, but there were substantial differences between laboratories, and the two-stage method gave significantly higher results than the one stage method. Of the technical variables in the one-stage method, only the activation time with one reagent appeared to have any influence on the results of this comparison of concentrate against plasma.

Accelerated degradation studies showed that the proposed standard is very stable. With the agreement of the participants, the material, in ampoules coded 80/556, has been established by the World Health Organization as the 3rd International Standard for Factor VIII :C, Concentrate, with an assigned potency of 3.9 iu/ampoule.

Keywords

Factor VIII - Concentrate - International Standard

• References

• 1 World Health Organization. Technical Report Series. 1977; 610: 12
• 2 Barrowcliffe TW, Tydeman MS, Kirkwood TB L, Thomas DP. Standardization of Factor VIII, III: Establishment of a stable reference plasma for Factor VIII-related activities. Thromb Haemostas 1983; 50
• 3 Barrowcliffe TW, Kirkwood TB L. An international collaborative assay for Factor VIII clotting activity. Thromb Haemostas 1978; 40: 260-271
• 4 Newman J, Johnson AJ, Karpatkin MH, Puszkin S. Methods for the production of clinically effective intermediate- and high-purity factor VIII concentrates. Br J Haematol 1971; 21: 1-41
• 5 Campbell PJ. International biological standards and reference preparations. II: Procedures used for the production of biological standards and reference preparations. J Biol Stand 1974; 2: 259-267
• 6 Biggs R, Eveling J, Richards G. The assay of antihaemophilic globulin activity. Br J Haematol 1955; 1: 20-34
• 7 Denson KW E. The simplified two-stage assay for factor VIII. In: Human Blood Coagulation, Haemostasis and Thrombosis. Biggs R. (ed) 2. Blackwell, Oxford; 1976. Appendix 2 688-689
• 8 Kirkwood TB, Snape TJ. Biometric principles in clotting and clot lysis assays. Clin Lab Haematol 1980; 2: 155-167
• 9 Bliss CI. The statistics of bioassay with special reference to the vitamins. Academic Press; New York: 1952
• 10 Kirkwood TB L. Geometric means and measures of dispersion. Biometrics 1979; 35: 908-909
• 11 Kirkwood TB L. Predicting the stability of biological standards and products. Biometrics 1977; 33: 736-742
• 12 Industry Collaborative Study Group. Assay of AHF concentrates and standards. Failure to eliminate variability with a monographed assay Thromb Res 1983; 30: 337-346
• 13 Kirkwood TB L, Barrowcliffe TW. Discrepancy between one-stage and two-stage assay of Factor VIII :C. Br J Haematol 1978; 40: 333-338
• 14 Lee ML, Magalang EA, Kingdon HS. An effect of pre-dilution on potency assays of factor VIII concentrates. Thromb Res 1983; 30: 511-519
• 15 Kasper CK. Problems with the potency of factor VIII concentrate. N Engl J Med 1981; 2: 50-51
• 16 Austen DE G, Rhymes IR, Rizza CR. Factor VIII concentrates: what the label says. Lancet 1981; 2: 1167
• 17 World Health Organization. Technical Report Series. 1983; 687: 24