Automation of Two-Stage Factor VIII Assay

Summary

Two automated methods for two-stage factor VIII assays have been compared with one another, and evaluated in practice. The Depex method records the clotting time when an electric circuit is completed by the formation of a fibrin thread across a hook-type electrode; the Electra method is based on an optical density technique of clot detection. The two methods gave comparable results for measured levels of factor VIII when haemophilic or “normal” plasmas were assayed. Results from the two methods in practice also suggest that both are valid at low and “normal” factor VIII levels. The Electra method is also probably suitable for assays of concentrates; however, the Depex method appears to give falsely high values in these circumstances, and experimental findings suggest that the reason may be that increased viscosity due to the high fibrinogen levels in factor VIII concentrates causes premature closure of the circuit between the two ends of the Depex electrode. The main advantage of the Depex method is that, provided 3 or 4 machines are available, a given number of assays can be completed more quickly than on Electra. The main advantages of Electra are that it is probably subject to less laboratory error than Depex, and that it is suitable for assaying concentrates as well as haemophilic and “normal” plasmas.

• References

• 1 Bangham DR, Biggs R, Brozović M, Denson KWE, Skeggs JL. 1971; A biological standard for measurement of blood coagulation factor VIII activity. Bulletin of the World Health Organization 45: 337
• 2 Barrowcliffe TW. 1977 Personal communication.
• 3 Biggs R, Eveling J, Richards G. 1955; Assay of antihaemophilic-globulin activity. British Journal of Haematology 1: 20
• 4 BrozoviĆ M, Stirling Y, Harricks C, North WRS, Meade TW. 1974; Factor VII in an industrial population. British Journal of Haematology 28: 381
• 5 Craske J. 1976 Personal communication.
• 6 Denson KWE. 1967. The simplified two-stage assay for factor VIII using a combined reagent. Transactions of the International Committee on Haemostasis and Thrombosis; Chapel Hill, North Carolina: 1966
• 7 Essien EM, Ingram GIC. 1967; Diagnosis of haemophilia: use of an artificial factor-VIII-deficient human plasma system. Journal of Clinical Pathology 20: 620
• 8 Farrell GW, Wolf P. 1971; The measurement of fibrinogen and its derivatives. I. Examination of methods of measurement of clottable fibrinogen. Journal of Medical Laboratory Technology 28: 310
• 9 Fearnley GR, Chakrabarti R. 1966; Fibrinolytic treatment of rheumatoid arthritis with phenformin and ethyloestranol. Lancet ii: 757
• 10 Finney DJ. 1963. In: Statistical Method in Biological Assay. Griffin; London:
• 11 Grant J, Biggs R. 1967. Experiments on the standardisation of the factor VIII assay. In: Brinkhous KM, Wright IS, Soulier JP, Roberts HR, Hinnom S. (Eds.) Platelets: Their role in haemostasis and thrombosis. F. K. Schattauer-Verlag, Stuttgart. Transactions of the International Committee on Haemostasis and Thrombosis; Chapel Hill, North Carolina: 1966
• 12 Hardisty RM, Mcpherson JC. 1962; An one-stage factor VIII (antihaemophilic globulin) assay and its use on venous and capillary plasma. Thrombosis et Diathesis Haemorrhagica 7: 215
• 13 Ingram GIC, North WRS. 1977 Personal communication.
• 14 Margolis J, Bruce S. 1964; An experimental approach to the kinetics of blood coagulation. British Journal of Haematology 10: 513
• 15 Meade TW, North WRS. 1977; Population based distribution of haemostatic variables. British Medical Bulletin 33: 283
• 16 Miller-Andersson M, Seghatchian MJ, Kirkwood TBL, Nilsson I. 1977 An automated assay technique for the routine evaluation of factor VIII concentrates. In preparation
• 17 Nyman D. 1970; The preparation of an artificial reagent for the one-stage factor VIII assay. Thrombosis et Diathesis Haemorrhagica 23: 206
• 18 Seghatchian MJ, Barrowcliffe T, Miller-ANDERSSON M. 1977; Adsorption of factor VIII on aluminium hydroxide. VIIth International Congress on Thrombosis and Haemostasis, Philadelphia. Thrombosis and Haemostasis 38: 24
• 19 Seghatchian MJ. 1977 Interaction between factor VIII and fibrinogen. Abstracts of IVth meeting International Society Haematology. Istanbul: