The International and “NIH” Units for Thrombin - How Do They Compare?

Summary

The current International Standard (IS) for α-thrombin was established in 1991. It was related in unitage with the 1st IS for Thrombin established in 1975 and contains 100 IU of thrombin activity. The National Institute of Health (NIH) standard (Lot J) is in common use for the calibration of commercial thrombin reagents and this study reports on a comparison of the thrombin units defined by these 2 standards. This study has indicated that one “NIH” unit is equivalent to 1.1 to 1.3 IU of thrombin, depending on the influence of PEG in the assay. A unitage ratio figure of 1.15 was recommended following analysis of data obtained in the presence and absence of PEG in the comparative assays. This was confirmed by amidolytic assay data.

• References

• 1 Robertson I, Gaffney PJ, Bangham DR. Standard For human thrombin. Thromb Diath Haemorrh 1975; 34: 3-19
• 2 Gaffney PJ. Thrombin and thrombin-like standards. Thromb Haemost 1977; 38: 562-566
• 3 Gaffney PJ, Heath AB, Fenton JWII. A collaborative study to establish an international standard for alpha-thrombin. Thromb Haemost 1992; 67: 424-427
• 4 Fenton II JW, Fasco MJ, Stackrow AB, Aronson DL, Young AM, Finlayson JS. Human thrombins. Production, evaluation and properties of α-thrombins J Biol Chem 1977; 252: 3587-3598
• 5 Campbell PJ. International Biologieals Standards and Reference Preparations. I. Preparation and presentation of materials to serve as standards and reference preparations J Biol Stand 1974; 2: 249-258
• 6 Finney DJ. Statistical Methods in Biological Assay. 3rd. Edition Griffin; London: 1978
• 7 Fenton JW, Fasco MJ. Polyethylene glycol 6,000 enhancement of the clotting of fibrinogen solutions in visual and mechanical assays. Thromb Res 1974; 4: 809-817
• 8 Ray MJ, Just SJ E, Carroll PA, Hawson GA T. A carryover artefact when using a recombinant thromboplastin on an automated coagulation analyse. Blood Coagulation Fibrinolysis 1994; 5: 315-316
• 9 Gaffney PJ, Lord K, Brasher M, Kirkwood TBL. Problems in the assay of thrombin using synthetic peptides as substrates. Thromb Res 1977; 10: 549-556