Paper-based dosing algorithms for maintenance of warfarin anticoagulation

We examined the quality of anticoagulation produced by two paper-based warfarin dosing algorithms in a randomized clinical trial of warfarin therapy. Fifty-eight patients were randomized to receive warfarin at a target international normalized ratio (INR) range of 2.1–3.0 and were followed for an average of 2.7 years. As a proportion of total patient-time, the percentage of time spent above, within, and below the therapeutic range was 11%, 71%, and 19% respectively. Fifty-six patients were randomized to receive warfarin at a higher target INR range (3.1–4.0) and had INRs within the therapeutic range for 40% of total patient time. We conclude that the performance, minimal cost, and ease-of-use of these algorithms make them well-suited for patient management within primary-care and research settings.

[1]  J. Knottnerus,et al.  Primary prevention of arterial thromboembolism in non-rheumatic atrial fibrillation in primary care: randomised controlled trial comparing two intensities of coumarin with aspirin , 1999, BMJ.

[2]  M. Kovacs,et al.  Randomized Assessment of a Warfarin Nomogram for Initial Oral Anticoagulation after Venous Thromboembolic Disease , 1998, Pathophysiology of Haemostasis and Thrombosis.

[3]  K. Hampton,et al.  A comparison of a low-dose warfarin induction regimen with the modified Fennerty regimen in elderly inpatients. , 2000, Age and ageing.

[4]  P. Sawicki,et al.  A structured teaching and self-management program for patients receiving oral anticoagulation: a randomized controlled trial. Working Group for the Study of Patient Self-Management of Oral Anticoagulation. , 1999, JAMA.

[5]  D. Witter,et al.  Quality of anticoagulation management among patients with atrial fibrillation: results of a review of medical records from 2 communities. , 2000, Archives of internal medicine.

[6]  R W Coleman,et al.  A Graphic Nomogram for Warfarin Dosage Adjustment , 1999, Pharmacotherapy.

[7]  David M. Smith,et al.  Risk of major hemorrhage for outpatients treated with warfarin , 1998, Journal of General Internal Medicine.

[8]  D. Anderson,et al.  Comparing the quality of oral anticoagulant management by anticoagulation clinics and by family physicians: a randomized controlled trial. , 2003, CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne.

[9]  J. Hirsh,et al.  The pharmacology and management of the vitamin K antagonists: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. , 2004, Chest.

[10]  R. Coleman,et al.  Nomogram for dosing warfarin at steady state. , 1991, Clinical pharmacy.

[11]  Michael Abdelnoor,et al.  Warfarin, aspirin, or both after myocardial infarction. , 2002, The New England journal of medicine.

[12]  F R Rosendaal,et al.  A Method to Determine the Optimal Intensity of Oral Anticoagulant Therapy , 1993, Thrombosis and Haemostasis.

[13]  J. Douketis,et al.  A comparison of two intensities of warfarin for the prevention of recurrent thrombosis in patients with the antiphospholipid antibody syndrome. , 2003, The New England journal of medicine.