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Thromb Haemost 2000; 84(06): 942-948
DOI: 10.1055/s-0037-1614153
Review Article
Schattauer GmbH

Issues with the Assay of Factor VIII Activity in Plasma and Factor VIII Concentrates

Roger L. Lundblad
1   From the Department of Pathology, University of North Carolina, Chapel Hill, USA
2   Baxter Healthcare – Hyland Immuno Division, Duarte, CA, USA
,
Henry S. Kingdon
3   Baxter Healthcare – Hyland Immuno Division (Lake Cook, IL), USA
,
Kenneth G. Mann
4   Department of Biochemistry, University of Vermont, Burlington, VT, USA
,
Gilbert C. White
5   Department of Medicine, Division of Hematology-Oncology, University of North Carolina at Chapel Hill, USA
› Author AffiliationsThe authors wish to thanks Drs. Gordon Bray, Edward Gomperts, Barry Woodham, Jerry Powell, Don Baker and Professor Hans Peter Schwarz for their helpful comments in the preparation of this manuscript.
Further Information

Publication History

Received 22 June 1999

Accepted after resubmission 03 August 2000

Publication Date:
13 December 2017 (online)

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Summary

A review of the literature suggests that assays accurate for the determination of factor VIII in plasma samples may not necessarily retain this accuracy when used for the determination of factor VIII in high-purity factor VIII concentrates such as Hemofil ® M. Review of assay data suggests that it is imperative to obtain maximal activation of the factor VIII in the sample with thrombin when using an assay system of isolated coagulation factors such as the two-stage assay or the various chromogenic substrate assays. Based on a combination of ease and reproducibility of performance and correlation of in vivo and in vitro measurements, it is recommended that the one-stage activated partial thromboplastin time performed with plasma from an individual with severe hemophilia A be used for the measurement of factor VIII potency. Chromogenic substrate assays can be used if care is taken to assure optimal activation of factor VIII by thrombin in the assay and the presence of sufficient factor IXa, phospholipid and calcium ions to stabilize factor Villa during the assay process.

Key words

Factor VIII - factor VIII assay/concentrates - chromogenic assays
 

  • References

  • 1 Hawkins TE, Green GJ, Romeril K, Milicih GS, Carter JM. Treatment of haemophilia a by continuous factor VIII infusion. Aust NZ J Med 1995; 25: 37-9.
    CrossrefPubMedSearch in Google Scholar
  • 2 Schulman S, Gitel S, Martinowitz U. Stability of factor VIII concentrates afterreconstitution. Amer JHematol 1994; 45: 217-23.
    PubMedSearch in Google Scholar
  • 3 Hurst D, Zabor S, Malianni D, Miller D. Evaluation of recombinant factor VIII (Kogenate®) stability for continuous infusion using a minipump infusion device. Haemophilia 1998; 04: 785-9.
    CrossrefPubMedSearch in Google Scholar
  • 4 Furie B, Limentani A. Rosenfeld CG A practical guide to the evaluation and treatment of hemophilia. Blood 1994; 84: 3-9.
    PubMedSearch in Google Scholar
  • 5 Carlsson MS, Stenberg PB, Bjornsson KA. Eklund LH Pharmaceutical services in the treatment of haemophilic patients. Amer J Hosp Pharm 1993; 50: 2073-6.
    PubMedSearch in Google Scholar
  • 6 Bangham DR, Biggs R, Brozovic M, Denson KWE, Skegg JL. A biological standard for measurement of blood coagulation factor VIII activity. Bull WHO 1971; 45: 337-51.
    PubMedSearch in Google Scholar
  • 7 Blomback M. et al. Nomenclature of quantities and units in thrombosis and haemostasis (Recommendation 1993). Thromb Haemost 1994; 71: 375-94.
    Thieme ConnectPubMedSearch in Google Scholar
  • 8 Barrowcliffe TW. Standards for factor VIII. Scand J Haematol 1980; 25 (Suppl. 37) 104-9.
    PubMedSearch in Google Scholar
  • 9 Kirkwood TBL. Problems in the standardization of factor VIII Assays. Scand J Haematol 1980; 25 (Suppl. 37) 110-5.
    PubMedSearch in Google Scholar
  • 10 Barrowcliffe TW, Raut S, Hubbard AR. Discrepancies in potency assessment of recombinant factor VIII concentrates. Haemophilia 1998; 04: 634-40.
    CrossrefPubMedSearch in Google Scholar
  • 11 Langdell RD, Wagner RH, Brinkhous KM. Effect of antihemophilic factor on one-stage clotting tests A presumptive assay for hemophilia and a simple one-stage antihemophilic factor assay procedure. J Lab Clin Med 1953; 41: 637-47.
    PubMedSearch in Google Scholar
  • 12 Over J. Methodology of the one-stage assay of factor VIII (VIII: C). Scand J Haematol 1986; 33 (Suppl. 41) 13-24.
    PubMedSearch in Google Scholar
  • 13 Dawson NJ, Kemball-Cook G, Barrowcliffe TW. Assay Discrepancies with Highly Purified Factor VIII Concentrates. Haemost 1989; 19: 131-7.
    CrossrefPubMedSearch in Google Scholar
  • 14 Feldman F, Chandra S, Hrinde M, Schreiber AB. Quality Assurance in Production of Plasma Proteins. In: Quality Assurance in Transfusion Medicine, Vol. II, Methodological Advances and Clinical Aspects. Rock G, Sejhatchian MJ. eds. Boca Raton, FL: CRC Press; 1993: 259-84.
    Search in Google Scholar
  • 15 Barrowcliffe TW, Watton J, Harmon A, Tubbs JF. Kemball-Cook G Potency of high purity factor VIII concentrates. Lancet 1990; ii: 124.
    PubMedSearch in Google Scholar
  • 16 Kemball-Cook G, Tubbs JE, Dawson NJ, Barrowcliffe TW. The behavior of different factor VIII concentrates in a chromogenic factor X-activating system. Brit J Haematol 1993; 84: 273-8.
    CrossrefPubMedSearch in Google Scholar
  • 17 Niemetz J, Nossel HL. Activated Coagulation Factors: In-Vivo and in-vivo Studies. Brit J Haematol 1969; 16: 337-51.
    CrossrefPubMedSearch in Google Scholar
  • 18 Assay of Blood Coagulation Factor VIII. European Pharmacopoeia. Third Edition. Strasbourg: Council of Europe; 1997. Section 2.7.4 111-3.
    Search in Google Scholar
  • 19 HoyerL W. The factor VIII complex: Structure and function. Blood 1981; 58: 1-13.
    PubMedSearch in Google Scholar
  • 20 Foster PA, Zimmerman TS. Factor VIII structure and function Blood 1989 Blood Reviews. 1989; 03: 180-91.
    PubMedSearch in Google Scholar
  • 21 Kane WH, Davie EW. Blood coagulation factors V and VIII: Structure and functional similarities and their relationships to hemorrhagic and thrombotic Disorders. Blood 1988; 71: 539-55.
    PubMedSearch in Google Scholar
  • 22 Chavin ST, Fay PJ. The Purification, Structure and Function of Factor VIII. In: Factor VHI-von Willebrand Factor. Sedgehatchian MJ: Savidge GF. eds. Boca Raton, FL: CRC Press; 1989: 2-23.
    Search in Google Scholar
  • 23 Fay PJ. Factor VIII Structure and Function. Thromb Haemost 1993; 70: 63-7.
    Thieme ConnectPubMedSearch in Google Scholar
  • 24 Lenting PJ, van Mourik JA, Mertens K. The life cycle of factor VIII in view of its structure and function. Blood 1998; 92: 3983-96.
    PubMedSearch in Google Scholar
  • 25 Rapaport SI, Schiffman S, Patch MJ, Ames SB. The importance of activation of antihemophilic globulin and proaccelerin by traces of thrombin in the generation of intrinsic prothrombinase activity. Blood 1963; 21: 221-36.
    PubMedSearch in Google Scholar
  • 26 Rapaport SI, Hjort PF, Patch MJ. Further evidence that thrombin-activa-tion of factor VIII is an essential step in intrinsic clotting. Scand J Clin Invest 1965; Suppl. 84: 88-100.
    PubMedSearch in Google Scholar
  • 27 Rick ME, Hoyer LW. Activation of low molecular weight fragment of antihemophilic factor (factor VIII) by thrombin. Nature 1974; 252: 404-5.
    CrossrefPubMedSearch in Google Scholar
  • 28 Rick M, Hoyer LW. Thrombin activation of factor VIII A comparison of purified factor VIII and the low molecular weight factor VIII procoagulant. Brit J Haematol 1978; 38: 107-19.
    CrossrefPubMedSearch in Google Scholar
  • 29 van Dieigen G, Tans G, Rosing J, Hemker HC. The role of phospholipid and factor Villa in the activation of bovine factor X. J Biol Chem 1981; 256: 3433-41.
    PubMedSearch in Google Scholar
  • 30 Krishnaswamy S, Church WE, Nesheim ME, Mann KG. Activation of Human Prothrombin by Human Prothrombinase Influence of factor Va on the reaction mechanism. J Biol Chem 1987; 262: 3291-9.
    CrossrefPubMedSearch in Google Scholar
  • 31 Jesty J. Interaction of feedback control and product inhibition in the activation of factor X by factors TXa and VIII. Haemost 1991; 21: 208-18.
    CrossrefPubMedSearch in Google Scholar
  • 32 Neuenschwander P, Jesty J. The use of acetylated factor X to prevent feedback activation of factor VIII during factor X activation: A tool for kinetic studies. Analyt Biochem 1990; 184: 347-52.
    CrossrefPubMedSearch in Google Scholar
  • 33 Bihoreau N, Sauger A, Yon JM, Van de Pol H. Isolation and characterization of different activated forms of factor VIII, the human antihaemophilic Afactor. Europ JBiochem 1989; 185: 111-8.
    PubMedSearch in Google Scholar
  • 34 Lollar P, Parker CG. Subunit structure of thrombin-activated porcine factor VIII. Biochemistry 1989; 28: 666-74.
    CrossrefPubMedSearch in Google Scholar
  • 35 Fay PJ, Haidoris P, Smudzin TM. Human factor Villa subunit structure Reconstitution of factor Villa from the isolated A1/A3-C1-C2 dimer and A2 subunit. J Biol Chem 1991; 266: 8957-62.
    PubMedSearch in Google Scholar
  • 36 Johnson DJD, Pemberton S, Acquila M, Mori PG, Tuddenham EGD, O’Brien DP. Factor VIII S373L: Mutation at PI’ site confers thrombin cleavage resistance causing mild haemophilia A. Thromb Haemost 1994; 71 (04) 428-33.
    Thieme ConnectPubMedSearch in Google Scholar
  • 37 Arai M, Inabe H, Higuchi M, Antonarakis SE, Kazazian Jr HH, Fujimaki M, Hoyer LE. Direct characterization of factor VIII in plasma: Detection of a mutation altering a thrombin cleavage site (arginine-372 → histidine. Proc Nat Acad Sci USA 1989; 86: 4277-81.
    CrossrefPubMedSearch in Google Scholar
  • 38 Pittman DD, Kaufmann PJ. Proteolytic requirements for thrombin activation of antihemophilic factor (Factor VIII). Proc Nat Acad Sci USA 1988; 85: 2429-33.
    CrossrefPubMedSearch in Google Scholar
  • 39 Hill-Eubanks DC, Parker CG, Lollar P. Differential proteolytic activation of factor VHI-von Willebrand factor complex by thrombin. Proc Nat Acad Sci USA 1989; 86: 6508-12.
    CrossrefPubMedSearch in Google Scholar
  • 40 Regan LM, Fay PJ. Cleavage of factor VIII light chain is required for maximal generation of factor Villa activity. J Biol Chem 1995; 270: 8546-52.
    CrossrefPubMedSearch in Google Scholar
  • 41 Neuenschwander P, Jesty J. A comparison of phospholipid and platelets in the activation of factor VIII by thrombin and factor Xa and in the activation of factor X. Blood 1988; 72: 1761-70.
    PubMedSearch in Google Scholar
  • 42 Lollar P, Knutson GJ, Fass DJ. Activation of porcine factor VIII: C by thrombin and factor Xa. Biochemistry 1985; 24: 8056-64.
    CrossrefPubMedSearch in Google Scholar
  • 43 Lamphear BJ, Fay PJ. Proteolytic interactions of factor IXa with human factor VIII and factor Villa. Blood 1992; 80: 3120-6.
    PubMedSearch in Google Scholar
  • 44 Switzer MEP, Pizzo SV, McKee PA. Is there a relatively procoagulant-inactive form of normal antihemophilic factor (Factor VIII)?. Blood 1979; 54: 916-27.
    PubMedSearch in Google Scholar
  • 45 Ofosu FA, Hirsh J, Esmon CT, Modi GJ, Smith LM, Anvari N, Buchanan MR, Fenton II MR, Blajchman MA. Unfractionated heparin inhibits throm-bin-catalyzed amplification reactions of coagulation more efficiently than those catalyzed by Factor Xa. Biochem J 1989; 257: 143-50.
    CrossrefPubMedSearch in Google Scholar
  • 46 Ofosu FA, Sie P, Modi GJ, Fernandez F, Buchanan MR, Blajchman MA, Boneu B, Hirsh J. The inhibition of thrombin-dependent positive-feedback reactions is critical to the expression of the anticoagulant effect of heparin. Biochem J 1987; 243: 579-88.
    CrossrefPubMedSearch in Google Scholar
  • 47 Broden K, Andersson L-O, Sandberg H. Kinetics of activation of human factor VIII by thrombin. Thromb Res 1980; 19: 299-307.
    CrossrefPubMedSearch in Google Scholar
  • 48 Pieters J, Lindhout T, Hempker HC. In situ-generated thrombin is the only enzyme that effectively activates factor VIII and factor V in thromboplastin-activated plasma. Blood 1989; 74: 1021-14.
    PubMedSearch in Google Scholar
  • 49 Jones KC, Mann KG. A model for the tissue factor pathway to thrombin II. A mathematical simulation. J Biol Chem 1994; 269: 23367-73.
    PubMedSearch in Google Scholar
  • 50 Butenas S, van’t Veer C, Mann KG. Evaluation of the initiation phase of blood coagulation using ultrasensitive assays for serine proteases. J Biol Chem 1997; 272: 21527-33.
    CrossrefPubMedSearch in Google Scholar
  • 51 Barrowcliffe TW, Tubbs JE, Wong MY. Evaluation of factor VIII deficient plasmas. Thromb Haemost 1993; 70: 433-7.
    Thieme ConnectPubMedSearch in Google Scholar
  • 52 Lee M, Maglalang EA, Kingdon HS. An effect of predilution on potency assays of factor VIII concentrates. Thromb Res 1983; 30: 511-9.
    CrossrefPubMedSearch in Google Scholar
  • 53 Frandsen H, Stender S, Scheibel E. An effect of predilution on VIII :C determination by the one-stage Assay. Thromb Res 1987; 48: 195-203.
    CrossrefPubMedSearch in Google Scholar
  • 54 Barrowcliffe TW. Recommendations for the assay of high-purity factor VIII concentrates. Thromb Haemost 1993; 70: 876-7.
    Thieme ConnectPubMedSearch in Google Scholar
  • 55 Mazurier C, Parquet-Gernez A, Goudemand M. Validation of a procedure for potency assessing of a high purity factor VIII concentrate Comparison of different factor VIII coagulant assays and effect of prediluent. Thromb Haemost 1990; 64: 251-5.
    Thieme ConnectPubMedSearch in Google Scholar
  • 56 Brinkhous KM, Sandberg H, Garris JB, Mattsson C, Palm M, Griggs MST. Purified human factor VIII procoagulant protein: Comparative hemostatic response after infusions into hemophilic and von Willebrand disease dogs. Proc Nat Acad Sci USA 1985; 82: 8752-6.
    CrossrefPubMedSearch in Google Scholar
  • 57 Giles AR, Tinlin S, Hoogendoorn H, Fournel MA, Ng P, Pancham N. In vivo characterization of recombinant factor VIII in a canine model of hemophilia A (factor VIII deficiency). Blood 1988; 72: 335-9.
    PubMedSearch in Google Scholar
  • 58 Fass DN, Bowie EJW, Owen Jr CA, Mann KG. Stability of porcine factor VIII. Thromb Res 1975; 06: 109-18.
    CrossrefPubMedSearch in Google Scholar
  • 59 Takese T, Rotblat F, Goodall AH, Kernoff PBA, Middleton S, Chand S, Denson KW, Austen DEG, Tuddenham EGD. Production of factor VIII deficient plasma by immunodepletion using three monoclonal antibodies. Brit J Haematol 1987; 66: 497-502.
    CrossrefPubMedSearch in Google Scholar
  • 60 Rothschild C, Amiral J, Adam M, Meyer D. Preparation of factor-VIII-deficient plasma with antibodies and its use for the assay of factor VIII. Haemost 1990; 20: 321-8.
    CrossrefPubMedSearch in Google Scholar
  • 61 Hill-Eubanks DC, Lollar P. vWF Is a cofactor for thrombin-catalyzed cleavage of the factor VIII light chain. JBiol Chem 1990; 265: 17854-8.
    PubMedSearch in Google Scholar
  • 62 Lollar P. The association of factor VIII with vWF. Mayo Clin Proc 1991; 66: 524-34.
    CrossrefPubMedSearch in Google Scholar
  • 63 Vukovich T, Koller E, Doleschel W. Low-molecular weight factor VIII requires a cofactor for its procoagulant activity. Thromb Res 1980; 503-11.
    PubMedSearch in Google Scholar
  • 64 Muntean W, Hathway WE, Montgomery RR. Influence of High-Molecular Weight Factor VIII on the Measurement of Low-Molecular Weight Factor VIII Procoagulant in Different Assay Systems. Brit J Haematol 1982; 51: 649-58.
    CrossrefPubMedSearch in Google Scholar
  • 65 Koedam JA, Hamer RJ, Beeser-Visser NH, Bouma BN, Sixma JJ. The effect of vWF on activation of factor VIII by factor Xa. Europ J Biochem 1990; 189: 229-34.
    CrossrefPubMedSearch in Google Scholar
  • 66 Koppelman SJ, Koedam JA, van Wijnen M, Stern DM, Nawroth PP, Sixma JJ, Bouma BN. vWF as a regulator of intrinsic factor X activation. JLab Clin Med 1994; 123: 585-93.
    PubMedSearch in Google Scholar
  • 67 Neuenschwander PF, Jesty J. Thrombin-activated and factor Xa-activated human factor VIII: Differences in cofactor activity and decay rate. Archs Biochem Biophys 1992; 296: 426-34.
    CrossrefPubMedSearch in Google Scholar
  • 68 Fricke WA, Yu WM-y. Characterization of vWF in factor VIII concentrates. Amer JHematol 1989; 31: 41-5.
    PubMedSearch in Google Scholar
  • 69 Mazurier C. Purification, Biochemistry, and Structure/Function Relationships of vWF. In: Factor VIII-vWF. Volume 1. Biochemical, Methodological and Functional Aspects. Seghatchian MJ, Savidge GF. eds. Boca Raton, FL: CRC Press; 1989: 41-81.
    Search in Google Scholar
  • 70 Seghatchian MJ. Regulatory Control, Standardization and Characterization of Clinical Concentrates. In: Factor VIII - vWF. Volume II. Clinical Aspects of Deficiency States. Seghatchian MJ, Savidge GF. eds. Boca Raton, FL: CRC Press; 1989: 223-53.
    Search in Google Scholar
  • 71 Aronson DL, Chang P. Ultracentrifugal analysis of factor VIII and von Willebrand Factor in therapeutic preparations. Vox Sang 1995; 69: 8-13.
    CrossrefPubMedSearch in Google Scholar
  • 72 Aronson DL, Chang P. Activated factor VIII in therapeutic preparations: Analysis by ultracentrifugation. Vox Sang 1996; 71: 142-9.
    CrossrefPubMedSearch in Google Scholar
  • 73 Brandt JT, Triplett DA. Laboratory Assays for Factor VIII. In: Coagulation and Bleeding Disorders. The Role of Factor VIII and vWF. Zimmerman TS, Rugged ZM. eds. New York: Marcel Dekker; 1989: 343-57.
    Search in Google Scholar
  • 74 Biggs R, Eveling J. Richards G The assay of antihaemophilic globulin. Brit J Haematol 1955; 01: 20-34.
    CrossrefPubMedSearch in Google Scholar
  • 75 Barrowcliffe T. Methodology of the two-stage assay of factor VIII (VIII :C). Scand J Haematol 1986; 33 (Suppl. 41) 25-38.
    PubMedSearch in Google Scholar
  • 76 Rosen S. Assay of factor VIII with a chromogenic substrate. Scand J Haematol 1984; 33 (Suppl. 40) 139-45.
    PubMedSearch in Google Scholar
  • 77 van Diejen G, van-Diegen-Visser MP, Franssen J, Hemker HC. Spectro-photometric method for the assay of human blood coagulation factor VIII. Haemostasis 1987; 17: 14-24.
    PubMedSearch in Google Scholar
  • 78 Hirst CF, Hewitt J, Poller L. Traces of factor VIII in substrate plasma. Brit J Haematol 1992; 81: 305-6.
    CrossrefPubMedSearch in Google Scholar
  • 79 Mann KG, Jenny RJ, Krishnaswamy S. Cofactor proteins in the assembly and expression of blood clotting enzyme complexes. Ann Rev Biochem 1988; 57: 915-56.
    CrossrefPubMedSearch in Google Scholar
  • 80 Silverberg M. The Assay of Coagulation Factors Using Synthetic Chromogenic Substrates. In: Methods in Hematology, Vol. 7. Disorders of Thrombin Formation. Colman RW. eds. New York: Churchill Livingstone; 1983: 1-23.
    Search in Google Scholar
  • 81 Andersson M, Andras M, Andersson N-E, Rosen S. Coamate® FVIII – a new kit for the accurate chromogenic determination of FVIII activity in plasma and concentrates on automated instruments or manually. Thromb Haemost 1993; 09: 1121 (abstract no. 2066)
    PubMedSearch in Google Scholar
  • 82 Lang H, Berreither M, Moritz B. A new chromogenic factor VHI-assay based on a system of human proteins. Thromb Haemost 1991; 65: 943 (abstract no. 882)
    PubMedSearch in Google Scholar
  • 83 Lee C, Barrowcliffe T, Bray G, Gomperts E, Hubbard A, Kemball-Cook G, Lilly P, Owens D, van Tilberg L, Pasi J. Pharmacokinetics in vivo comparison of using 1-stage and chromogenic substrate assays with two formulations of Hemofil® M. Thromb Haemost 1996; 76: 950-6.
    Thieme ConnectPubMedSearch in Google Scholar
  • 84 Nilsson FM, Kirkwood TBL, Barrowcliffe TW. In vivo recovery of factor VIII: A comparison of one-stage and two-stage assay methods. Thromb Haemost 1979; 42: 1230-9.
    Thieme ConnectPubMedSearch in Google Scholar
  • 85 Hellstern P, Kiehl R, Myashita C, Scherdt H, von Blohn G, Kohler M, Biittner M, Wenzel E. Factor VIII :C (FVIII :C) recovery and half-life after infusion of steam-treated high-purity factor VIII concentrate in severe hemophilia A A comparison of one-stage assay, two-stage assay and a chromogenic substrate assay. Thromb Haemost 1986; 56: 353-9.
    Thieme ConnectPubMedSearch in Google Scholar
  • 86 Messori A, Morfini M, Blomback M, Cinotti S, Longo G, Schimpf K, Schumacher K, Novakova-Banet A, Delvos U, Kjellman H. Pharmacokinetics of two pasteurized factor VIII concentrates by different and multi-center assays of factor VIII activity. Thromb Res 1992; 65: 699-708.
    CrossrefPubMedSearch in Google Scholar
  • 87 Blomback M, Kjellman H, Main JP, Hedner U, Schimpf K, Weichel B. On the unreliability of one-stage factor VIII: C clotting assays after infusion of factor VIII concentrates. Scand J Clin Lab Invest 1987; 47: 561-6.
    CrossrefPubMedSearch in Google Scholar
  • 88 Barrowcliffe TW. Standardization and Assay. Sem Thromb Hemost 1993; 19: 73-9.
    Thieme ConnectPubMedSearch in Google Scholar
  • 89 Ofosu FA, Blajchman MA, Barr R, Inwood M. Approaches to the Measurement of the In Vivo Response to Factor VIII Concentrate Infusion. Thromb Res 1985; 42: 471-6.
    PubMedSearch in Google Scholar
  • 90 Matucci M, Messori A, Donati-Cori G, Longo G, Vannini S, Morfini M, Tendi E, Rossi-Ferrini PL. Kinetic evaluation of four Factor VIII concentrates by model-independent methods. Scand J Haematol 1985; 34: 22-8.
    PubMedSearch in Google Scholar
  • 91 Longo G, Matucci M, Messori A, Morfini M, Rossi-Ferrini PL. Pharmacokinetics of a new heat-treated concentrate of factor VIII estimated by model-independent methods. Thromb Res 1986; 42: 471-6.
    CrossrefPubMedSearch in Google Scholar
  • 92 White II GC, McMillan CW, Kingdon HS, Shoemaker CB. Use of recombinant antihemophilic factor in the treatment of two patients with classic hemophilia. NewEng J Med 1989; 320: 166-70.
    PubMedSearch in Google Scholar
  • 93 Schwartz RD. et al. Human recombinant DNA-derived antihemophilic factor (factor VIII) in the treatment of hemophilia A. New Eng J Med 1990; 323: 1800-5.
    CrossrefPubMedSearch in Google Scholar
  • 94 Morfini M, Lee M, Messori A. The design and analysis of half-life and recovery studies for factor VIII and factor IX. Thromb Haemost 1991; 66: 384-6.
    Thieme ConnectPubMedSearch in Google Scholar
  • 95 Morfin M, Mannucci PM, Longo G, Cinotti S, Messori A. Comparative evaluation of the pharmacokinetics of three monoclonal factor VIII concentrates. Thromb Res 1991; 61: 285-90.
    CrossrefPubMedSearch in Google Scholar
  • 96 Addiego JE, Gomperts E, Liu S-L, Bailey P, Courier SG, Lee ML, Neslund GG, Kingdon HS, Griffith MJ. Treatment of hemophilia A with a highly purified factor VIII concentrate prepared by anti-FVIIIc immuno-affmity chromatography. Thromb Haemost 1992; 67: 19-27.
    Thieme ConnectPubMedSearch in Google Scholar
  • 97 Manno CS, Butler RB, Cohen AR. Low recovery in vivo of highly purified factor VIII in patients with hemophilia. J Pediat 1992; 12: 814-8.
    PubMedSearch in Google Scholar
  • 98 Bjorkman S, Carlsson M, Berntorp E, Stenberg P. Pharmacokinetics of factor VIII in humans Obtaining clinically relevant data from comparative studies. Clin Pharmacokinetics 1992; 22: 385-95.
    CrossrefPubMedSearch in Google Scholar
  • 99 Morfini M. et al. Pharmacokinetic properties of recombinant factor VIII compared with a monoclonally purified concentrate (Hemofil M®). Thromb Haemost 1992; 68: 433-5.
    Thieme ConnectPubMedSearch in Google Scholar
  • 100 Knvellman A, de Wit HJC, Potstra P, Does vdJA. Development and small-scale production of a severely heated factor VIII concentrate. Vox Sang 1994; 66: 89-95.
    CrossrefPubMedSearch in Google Scholar
  • 101 Woodrow IE, Manson GA. A general expression for coupled enzyme assays of hysteretic enzymes. Biochem J 1984; 220: 173-8.
    CrossrefPubMedSearch in Google Scholar
  • 102 Brooks SP, Suelter CH. Lagtime, a program for calculating coupled enzyme assay parameters. Intern J Biomed Comput 1986; 19: 101-7.
    PubMedSearch in Google Scholar
  • 103 Yang SY, Schultz H. Kinetics of coupled enzyme reactions. Biochemistry 1987; 26: 5579-84.
    CrossrefPubMedSearch in Google Scholar
  • 104 Sergienko EA, Srivastava DK. A continuous spectrophotometric method for the determination of glycogen phosphorylase-catalyzed reaction in the direction of glycogen synthesis. Analyt Biochem 1994; 221: 348-55.
    CrossrefPubMedSearch in Google Scholar
  • 105 Barrowcliffe TW, Raut A, Hubbard AR. Discrepancies in potency assessment of recombinant FVIII concentrates. Haemophililia 1998; 04: 634-40.
    PubMedSearch in Google Scholar
  • 106 Lind P, Larsson K, Spira J, Sydow-Backman M, Almstedt A, Gray E, Sandberg H. Novel forms of B-domain-deleted recombinant factor VIII molecules Construction and biochemical characterization. Eur J Biochem 1995; 232: 19-27.
    CrossrefPubMedSearch in Google Scholar
  • 107 Fatouros A, Osterberg T, Mikaelsson M. Recombinant factor VIII SQ -inactivation kinetics in aqueous solution and the influence of disacchari-des and sugar alcohols. Pharmaceutical Research 1997; 14: 1679-84.
    CrossrefPubMedSearch in Google Scholar
  • 108 Osterberg T, Fatouros A, Mikaelsson M. Development of freeze-dried albumin-free formulation of recombinant factor VIII SQ. Pharmaceutical Research 1997; 14: 892-8.
    CrossrefPubMedSearch in Google Scholar
  • 109 Lusher JM, Hillman-Wiesman C, Horst D. In vivo recovery with products of very high purity – assay discrepancies. Haemophilia 1998; 04: 641-5.
    CrossrefPubMedSearch in Google Scholar
  • 110 Mikaelsson M, Oswaldsson U, Sandberg H. Influence of phospholipids on the assessment of factor VIII activity. Haemophilia 1998; 04: 646-50.
    CrossrefPubMedSearch in Google Scholar
  • 111 Pittman DP, Alderman EM, Tomkinson KW, Wang JH, Giles AR, Kauf-mann RJ. Biochemical, immunological, and in vivo functional characterization of B-domain deleted factor VIII. Blood 1993; 81: 2925-35.
    PubMedSearch in Google Scholar
  • 112 Merens K, Donath MJSH, van Leen RW, de Keyzer-Nellen MJM, Verbeet MPh, Klaase JMBos, Leyte A, van Mourik JA. Biological activity of recombinant factor VIII variants lacking the central B-domain and the heavy-chain sequence Lys713-Arg740: discordant in vitro and in vivo activity. Brit J Haematol 1993; 85: 133-42.
    CrossrefPubMedSearch in Google Scholar
  • 113 Finney DJ. Statistical Method in Biological Assay. 3rd Edition. New York: Macmillan Publishing Co., inc; 1978
    Search in Google Scholar