Standardization of Low Molecular Weight Heparins : A Collaborative Study

Summary

A collaborative study was carried out, in which eight laboratories each assayed eight low molecular weight (LMW) heparins against the International Standard (IS) for heparin. APTT assays and three types of anti-Xa method were used. The results of this study showed that:

1. LMW heparins cannot be validly assayed against the IS by APTT or anti-Xa methods.

2. Potencies of LMW heparins vs. the IS differed considerably between the four types of assay method used and also between different laboratories using the same type of method.

3. Adoption of a single LMW heparin standard would improve validity, improve inter-laboratory variation, and largely abolish the differences between the three types of anti-Xa method. However, since calibration of a LMW heparin standard against the IS would give potencies that differ widely by the different assay methods, a single assay method such as the anti-Xa amidolytic, plasma, would need to be chosen for this calibration.

Keywords

LMW heparin - Assay - Standards

• References

• 1 Johnson EA, Kirkwood TBL, Stirling Y, Perez-Requejo JL, Ingram G IC, Bangham DR, Brozovic M. Four heparin preparations: anti-Xa-potentiating effect of heparin after subcutaneous injection. Thromb Haemostas 1976; 35: 586-591
• 2 Andersson L-O, Barrowcliffe TW, Holmer E, Johnson EA, Sims G EC. Anticoagulant properties of heparin fractionated by affinity chromatography on matrix-bound antithrombin III and by gel filtration. Thromb Res 1976; 9: 575-583
• 3 Lane DA, MacGregor IR, Michalski R, Kakkar VV. Anticoagulant activities of four unfractionated and fractionated heparins. Thromb Res 1978; 12: 257-271
• 4 Barrowcliffe TW, Johnson EA, Eggleton CA, Kemball-Cook G, Thomas DP. Anticoagulant activities of high and low molecular weight heparin fractions. Br J Haematol 1979; 41: 573-583
• 5 Holmer E, Kurachi K, Soderstrom G. The molecular-weight dependence of the rate-enhancing effect of heparin on the inhibition of thrombin, factor Xa, factor IXa, factor XIa, factor Xlla and kallikrein by antithrombin. Biochem J 1981; 193: 395-400
• 6 Holmer E, Lindahl U, Backstrom G, Thunberg L, Sandberg H, Soderstrom G, Andersson L-O. Anticoagulant activities and effects on platelets of a heparin fragment with high affinity for antithrombin. Thromb Res 1980; 18: 861-869
• 7 Salzman EW, Rosenberg RD, Smith MH, Lindon JN, Favreau L. Effect of heparin and heparin fractions on platelet aggregation. J Clin Invest 1980; 65: 64-73
• 8 Carter CJ, Kelton JG, Hirsh J, Cerskus A, Santos AV, Gent M. The relationship between the haemorrhagic and antithrombotic properties of low molecular weight heparin in rabbits. Blood 1982; 59: 1239-1245
• 9 van Rutten J, van de Ruit M, Beunis M, Hemker HC. Determination of low molecular weight heparin in clinical laboratory. Haemostasis 1984; 14: 205-210
• 10 Yin ET, Wessler S, Butler JV. Plasma heparin: a unique, practical, submicrogram-sensitive assay. J Lab Clin Med 1973; 81: 298-305
• 11 Denson K WE, Bonnar J. The measurement of heparin: a method based on the potentiation of anti-factor Xa. Thrombos Diathes Haemorrh 1973; 30: 471-479
• 12 Eggleton CA, Barrowcliffe TW, Merton RE, Thomas DP. In vitro and in vivo studies of the anti-Xa activity of heparin. Thromb Res 1981; 24: 319-328
• 13 Armitage P. Statistical Methods in Medical Research. Blackwell; Oxford: 1971: 205-207
• 14 Finney DJ. Statistical Method in Biological Assay. 3rd ed Griffin; London: 1978
• 15 Thomas DP, Curtis AD, Barrowcliffe TW. A collaborative study designed to establish the 4th International Standard for heparin. Thromb Haemostas 1984; 52: 148-153
• 16 Kakkar VV, Djazavi B, Fok J, Fletcher M, Scully MF, Westwick J. Low molecular weight heparin and prevention of post-operative deep vein thrombosis. Br Med J 1982; 284: 375-379
• 17 Roussi JH, Houbouyan LL, Goguel AF. Use of low-molecular-weight heparin in heparin-induced thrombocytopenia with thrombotic complications. Lancet 1984; 1: 1183
• 18 Schmitz-Huebner U, Bünte H, Freise G, Reers B, Rüschemeyer C, Scherer R, Schulte H, van de Loo J. Clinical efficacy of low molecular weight heparin in postoperative thrombosis prophylaxis. Klin Wochenschr 1984; 62: 349-353
• 19 Massonet-Castel S, Pelissier E, Dreyfus G, Deloche G, Abry B, Guibourt P, Terrier E, Passelecq JM, Jaulmes B, Carpentier A. Low-molecular-weight heparin in extra-corporeal circulation. Lancet 1984; 1: 1182