A Comparison of Heparin Potency Estimates Obtained by Activated Partial Thromboplastin Time and British Pharmacopoeial Assays

Summary

Heparin samples from five manufacturers were assayed by the revised British Pharmacopoeia (BP) heparin assay and the results compared with those obtained using the activated partial thromboplastin time (APTT) assay. The United States Pharmacopeia (USP) reference heparin preparation and the 4th International Standard (IS) for heparin were also assayed by the two methods relative to the 3rd IS. The results obtained by the revised BP assay were in close agreement with those obtained by the APTT assay for all the heparins that were tested. The assays revealed that there is at least a 10% discrepancy between the International Unit for heparin and the USP unit.

Key words

In vitro heparin assays - APTT - BP assay

• References

• 1 British Pharmacopoeia, Appendix XIV D, A54-5, 1980, Addendum. 1983
• 2 British Pharmacopoeia, Appendix XV G. 1953; pp 833-834
• 3 Proctor RR, Rapaport SI. A partial thromboplastin time with kaolin. A simple screening test for first stage plasma clotting factor deficiencies Am J Clin Pathol 1961; 36: 212-219
• 4 Finney DJ. Statistical Methods in Biological Assay. 3. Edit, Griffin London: 1978
• 5 Thomas DP, Curtis AD, Barrowcliffe TW. A collaborative study designed to establish the 4th International Standard for Heparin. Thromb Haemostas 1984; 52: 148-153
• 6 Poller L, Thomson JM. Standardisation of prothrombin time and partial thromboplastin time. In Disorders of Thrombin Formation. Robert WColman. (Ed) Churchill Livingstone; Edinburgh: 1983. pp 53-83
• 7 Gomperts ED, Zucker ML. Heparin, brain thromboplastin and the insensitivity of the prothrombin time to heparin activity. Thromb Res 1977; 12: 105-117
• 8 Levine SP, Wohl H. Human platelet factor 4: purification and characterization by affinity chromatography. J Biol Chem 1976; 251: 324-328
• 9 The United States Pharmacopeia, XX, National Formulary XV. 1980; p 365