Anti Xa Monitoring during Treatment with Low Molecular Weight Heparin or Danaparoid: Inter-assay Variability

Summary

If laboratory monitoring of low molecular weight heparin (LMWH) therapy is required the test of choice is the anti Xa activity assay. The relationship between anti Xa results obtained using different techniques is unknown. The aim of the present study was to compare anti Xa results obtained with eight different commercially available anti Xa activity assays (five chromogenic and three clotting based assays) in samples from patients receiving either therapeutic or prophylactic LMWH (enoxaparin or dalteparin) or danaparoid.

We have demonstrated that highly significant differences exist between results obtained using different techniques. The mean anti Xa activity in patients receiving treatment or prophylaxis with enoxaparin ranged from 0.28 to 0.64 iu/ml. A similar relationship was present in samples from patients treated with dalteparin, mean anti Xa results ranging from 0.43 to 0.69 iu/ml. The Heptest clotting assay as used here in combination with the Automated Coagulation Laboratory instrument, was associated with lower results than other clotting or chromogenic techniques. In patients receiving danaparoid for heparin induced thrombocytopaenia (HIT) mean results with three clotting based assays were 0.30 to 0.36 u/ml, compared to mean results of 0.47 to 0.65 u/ml for chromogenic assays.

Our data clearly indicate that the selection of anti Xa assay method could influence patient management since the dose required to achieve the therapeutic range would differ according to the assay employed. This is particularly important since the frequency of hamorrhagic side effects has been shown by others to be dose dependant, irrespective of the concomitant anti Xa activity results. In danaparoid therapy the clotting assays studied here should not be employed for monitoring without a modified target range, unless it can be demonstrated that the higher doses required to achieve the therapeutic range are safe.

¹ Present address: Dr. R. Iampietro, National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Potters Bar, EN6 3QG, UK

• References

• 1 Hull RD, Pineo GF. Low molecular weight heparin treatment of venous thromboembolism. Prog Card Diseases 1994; 37: 71-4.
• 2 Boneu B. Low Molecular Weight Heparin Therapy: Is monitoring needed?. Thromb Haemost 1994; 72: 330-4.
• 3 Simonneau G, Sors H, Charbnnier B, Page Y, Laaban JP, Azarian R, Laurent M, Hirsch JL, Ferrari E, Bosson JL, Mottier D, Beau B. A comparison of Low Molecular Weight Heparin with Unfractionated Heparin for Acute Pulmonary Embolism. N E J Med 1997; 337: 663-9.
• 4 Fragmin during Instability in coronary artery disease (FRISC) study group. Low molecular weight heparin during instability in coronary artery disease. Lancet 1996; 347: 561-8.
• 5 Cohen M, Demers C, Gurfinkel EP, Turpie AGG, Fromell GJ, Goodman S, Langer A, Califf RM, Fox KAA, Premmereur J, Bigonzi F. A comparison of LMWH with unfractionated heparin for unstable coronary artery disease. New Eng J Med 1997; 337: 447-52.
• 6 Handeland GF, Abildgaard U, Holm HA, Arnesen KA. Dose adjusted heparin treatment of deep venous thrombosis: a comparison of unfractionated and low molecular weight heparin. Eur J Clin Pharm 1990; 39: 107-12.
• 7 Boneu B, Buchanan MR, Caranobe C, Gabaig AM, Dupouy D, Sie P, Hirsh J. The disappearance of a low molecular weight heparin fraction (CY216) differs from standard heparin in rabbits. Thromb Research 1987; 46: 845-53.
• 8 Bara L, Combe-Tamzali S, Conard J, Horellou MH, Samama M. Laboratory monitoring of a low molecular weight heparin (Enoxaparine) with a new clotting test (Heptest). Haemostasis 1987; 17: 127-33.
• 9 Sie P, Aillaud MF, De prost D, Drouille C, Forestier F, Guedi P, Juhan-Vague I, Polack B, Potron G, Roncato M, Roussi J, Sampol J, Aiach M. Measurement of low molecular weight heparin ex vivo activities in clinical laboratories using various anti Xa assays: interlaboratory agreement and requirement for an agreed low molecular weight heparin standard. Thromb Haemost 1987; 58: 879-83.
• 10 Houbouyan LL, Boutiere B, Contant G, Dautzenberg MD, Fievet P, Potron G, Vassault A, Gourmelin Y. Validation protocol of analytical haemostasis systems: measurement of anti Xa activity of low molecular weight heparins. Clin Chem 1996; 42: 1223-30.
• 11 Kessler CM, Esparranguera IM, Jacobs HM, Druy E, Fortune WP, Holloway SD, Giordano J, Davidson B. Monitoring the anticoagulant effects of a low molecular weight heparin: correlation of assays in orthopaedic surgery patients receiving ardeparin sodium for prophylaxis of deep venous thrombosis. Am J Clin Path 1995; 103: 642-8.
• 12 Boneu B, Faruel-Bille V, Pierrejean D, Gabaig AM. Limitations of the chromogenic assays to determine plasma antifactor Xa activity during low molecular weight heparin therapy. Nouv Rev Fr Haematol 1991; 33: 287-91.
• 13 Magnani HN. Heparin induced thrombocytopaenia: an overview of 230 patients treated with orgaran (Org 10172). Thromb Haemost 1993; 70: 554-61.
• 14 Ozawa T, Domagalski J, Mammen EF. Determination of Low molecular Weight Heparin by Heptest on the Automated Coagulation Laboratory system. Am J Clin Pathol 1993; 99: 157-62.
• 15 Nieuwenhuis HK, Albada J, Banga JD, Sixma JJ. Identification of risk factors for bleeding during treatment of acute venous thromboembolism with heparin or low molecular weight heparin. Blood 1991; 78: 2337-43.
• 16 Turpie AGG, Levine MN, Hirsh J, Carter CJ, Jay RM, Powers PJ, Andrew M, Hull RD, Gent M. A randomised controlled trial of a low molecular weight heparin (enoxaparin) to prevent deep vein thrombosis in patients undergoing elective hip surgery. New Engl J Med 1986; 315: 925-9.
• 17 Dawes J, Bara L, Billaud E, Samama M. Relationship between biological activity and concentration of a low molecular weight heparin (PK 10169) and unfractionated heparin after intravenous and subcutaneous administration. Haemostasis 1986; 16: 116-22.
• 18 Frydman AM, Bara L, Le Roux Y, Woler M, Chauliac F, Samama MM. The antithrombotic activity and pharmacokinetics of enoxaparin, a low molecular weight heparin, in humans given single subcutaneous doses of 20 to 80 mg. J Clin Pharmacol 1988; 28: 609-18.
• 19 Laforest MD, Colas-Linhart N, Guiraud-Vitaux F, Bok B, Bara L, Samama M, Marin J, Bault F, Uzan A. Pharmacokinetics and biodistribution of technetium 99m labelled standard heparin and a low molecular weight heparin (enoxaparin) after intravenous injection in normal volunteers. Br J Haem 1991; 77: 201-8.
• 20 Levine MN, Plasnes A, Hirsh J, Goodyear M, Vochelle N, Gent M. The relationship between anti factor Xa and clinical outcome in patients receiving enoxaparine low molecular weight heparin to prevent deep vein thrombosis after hip replacement. Thromb Haemost 1989; 62: 940-4.
• 21 Holmstrom MC, Berglund S, Granquist S, Bratt G, Tornebohm E, Lockner D. Fragmin once or twice daily subcutaneously in the treatment of deep venous thrombosis of the leg. Thromb Research 1992; 67: 49-55.
• 22 Simonneau G, Bergman JF, Kher A, Soria C, Tobelem G. Pharmacokinetics of a low molecular weight heparin (Fragmin) in young and elderly subjects. Thromb Research 1992; 66: 603-7.
• 23 Abildgaard U, Nottheim L, Larsen AE. Monitoring therapy with low molecular weight heparin: a comparison of 3 chromogenic substrate assays and the Heptest clotting assay. Haemost 1990; 20: 193-200.
• 24 Harenberg J, Huck K, Bratsch H, Stehle G, Demplfle CE, Mall K, Blauth M, Usadel KH, Heene DL. Therapeutic application of subcutaneous low molecular weight heparin in acute venous thrombosis. Haemostasis 1990; 20 (suppl) 205-19.
• 25 Kitchen S, Jennings I, Woods TAL, Preston FE. Wide variability in the sensitivity of APTT reagents for monitoring of heparin dosage. J Clin Path 1996; 49: 10-4.
• 26 Dignac M, Gabaig AM, Cambus JP, Boneu B. A new chronometric assay to determine plasma antifactor Xa activity which is insensitive to the antithrombin activity of low molecular weight heparin. Nouv Rev Fr Hematol 1993; 35: 545-9.
• 27 Briant L, Caranobe C, Saivin S, Sie P, Bayrou B, Houin G, Boneu B. Unfractionated heparin and CY216: pharmacokinetics and bioavailabilities of the anti Xa and IIa effects after intravenous and subcutaneous injection in the rabbit. Thromb Haemost 1989; 61: 348-53.
• 28 Hemker H, Beguin S, Bendetowicz A, Wielders S. The determination of the levels of unfractionated heparin and low molecular weight heparins in plasma. Their effect on thrombin mediated feedback reactions in vivo. Preliminary results on samples after subcutaneous injection. Haemostasis 1991; 21: 258-72.
• 29 Warkentin TE, Chong BH, Greinacher A. Heparin-induced Thrombocytopaenia: Towards consensus. Thromb Haemost 1998; 79: 1-7.
• 30 Danhof M, de Boer A, Magnani HN, Steikema JAJ. Pharmacokinetic considerations on Orgaran (Org 10172) therapy. Haemostasis 1992; 22: 73-84.
• 31 Meuleman DG. Orgaran (org 10172): Its Pharmacological profile in experimental models. Haemostasis 1992; 22: 58-65.