Assessment of Therapeutic Quality Control in a Long-Term Anticoagulant Trial in Post-Myocardial Infarction Patients

Summary

Various methods have been described to evaluate efficacy of anticoagulant therapy using the international normalized ration (INR). We compared the following approaches: (1) total INR’s or the most recent measurement; (2) percent time within therapeutic range, with INR changing directly or halfway between visits; and (3) total observation time assuming INR changing linearly. The study population comprised 1700 post myocardial infarction patients. Treatment comprised 3725 patient-years. There were 61,471 INR assessments with target therapeutic level of 2.8–4.8. Acenocoumarol as well as phenprocoumon were employed. Therapeutic achievement in the first months of treatment was low: less than 60% of INR’s were in range. Treatment stabilized after 6 months. Patients on acenocoumarol were within range 70% of the time compared to 80% for phenprocoumon. Method 3 is preferred because it incorporates time and is capable of calculating incidence rates at different INR levels. Our findings call for an urgent improvement of standard of anticoagulant control in the first months following commencement of treatment.

• References

• 1 Hirsh J. Oral anticoagulant drugs. N Engl J Med 1991; 324: 1865-1875
• 2 Poller L, Hirsh J. Optimal therapeutic ranges for oral anticoagulation. In: Thrombosis in cardiovascular disorders Fuster V, Verstraete M. eds Philadelphia: W. B. Saunders Company; 1992: 161-73
• 3 vd Meer FJM, Rosendaal FR, Vandenbroucke JP, Briet E. Bleeding complications in oral anticoagulant therapy: an analysis of risk factors. Arch Intern Med 1993; 153: 1557-1562
• 4 Kirkwood TBL. Calibration of reference thromboplastins and standardisation of the prothrombin time ratio. Thromb Haemost 1983; 49: 238-244
• 5 Loeliger EA. ICSH/ICTH recommendations for reporting prothrombin time in oral anticoagulant control. Thromb Haemost 1985; 53: 155-156
• 6 Loeliger EA: Laboratory control, optimal therapeutic ranges and therapeutic quality control in oral anticoagulation. Acta Haematol 1985; 74: 125-131
• 7 Loeliger EA, Broekmans AW. Optimal therapeutic anticoagulation. Haemostasis 1985; 15: 283-292
• 8 Poller L. Optimal therapeutic range for oral anticoagulation. In: Recent advances in blood coagulation Poller L. ed Edinburgh: Churchill Livingstone; 1991: 245-264
• 9 Davis FB, Estruch MT, Samson-Corvera EB, Voigt GC, Tobin JD. Management of anticoagulation in outpatients. Experience with ananticoagulation service in a municipal hospital setting. Arch Intern Med 1977; 137: 197-202
• 10 Forfar JC. A 7-year analysis of haemorrhage in patients on long-term anticoagulant treatment. Br Heart J 1979; 42: 128-132
• 11 Harries AD, Birtwell AJ. Jones DB: Anticoagulant control. Letter to the editor. Lancet 1981; 2: 1320
• 12 The Sixty Plus Reinfarction Study Research Group. A double-blind trial to assess long-term oral anticoagulant therapy in elderly patients after myocardial infarction. Lancet 1980; 2: 989-993
• 13 Mclnnes GT. Efficacy of anticoagulation in the U. K. Letter to the editor. Lancet 1981; 2: 88
• 14 Majumdar G, Payne RW. Quality of oral anticoagulant therapy. Clin Lab Haematol 1985; 7: 125-131
• 15 Wickramasinghe LSP, Basu SK, Bansal SK. Long-term oral anticoagulant therapy in elderly patients. Age and Ageing 1988; 17: 388-396
• 16 Smith P, Arnesen H, Holme I. The effect of warfarin on mortality and reinfarction after myocardial infarction. N Engl J Med 1990; 323: 147-152
• 17 van den Besselaar AMPH, van der Meer FJM, Gerrits-Drabbe CW. Therapeutic control of oral anticoagulant treatment in the Netherlands. Am J Clin Pathol 1988; 90: 685-690
• 18 van den Besselaar AMPH. Recommended method for reporting therapeutic control of oral anticoagulant therapy. Thromb Haemost 1990; 63: 316-317
• 19 Broekmans AW, Loeliger EA. Therapeutic control of anticoagulant treatment. Letter to the editor. Br Med J 1982; 284: 1330-13331
• 20 Duxbury BMcD. Therapeutic quality control leading to further clinical assessment of oral anticoagulation. Acta Haematol 1986; 76: 65-67
• 21 Duxbury BMcD. Therapeutic control of anticoagulant treatment. Letter to the editor. Br Med J 1982; 284: 1634-1635
• 22 Copplestone A, Roath S. Assessment of therapeutic control of anticoagulation. Acta Haematol 1984; 71: 376-380
• 23 Raper CGL. The therapeutic control of anticoagulant clinics. Letter to the Editor. Clin Lab Haematol 1983; 5: 325-327
• 24 Rosendaal FR, Cannegieter SC, vd Meer FJM, Briet E. A method to determine the optimal intensity of oral anticoagulant therapy. Thromb Haemost 1993; 69: 236-239
• 25 Cannegieter SC, Rosendaal FR, Briet E. The optimal intensity of oral anticoagulant therapy in patients with prothetic heart valves (abstract). Thromb Res 1992; 65: 80
• 26 Anticoagulants in the Secondary Prevention of Events in Coronary Thrombosis (ASPECT) Research group. Effect of long-term anticoagulant treatment on mortality an cardiovascular morbidity after myocardial infarction. Lancet 1994; 1: 499-503
• 27 Loeliger EA, Lewis SM. Progress in laboratory control of oral anticoagulants. Lancet 1982; 2: 318-320
• 28 Rozenberg MC, Kronenberg H, Firkin BG. “Thrombotest” and prothrombin time: a controlled clinical trial. Aust Ann Med 1965; 14: 3-12
• 29 Wiegeman H, Vossepoel AM. A computer program for long-term anticoagulation control. Comput Programs Biomed 1977; 7: 71-84
• 30 Walker SH, Duncan DB. Estimation of the probability of an event as a function of several independent variables. Biometrika 1967; 54: 167-179
• 31 Azar AJ. Therapeutic achievement with long-term oral anticoagulants in post myocardial infarction patients.Dissertation. Erasmus University Rotterdam, The Netherlands 1993
• 32 Fekkes N, de Jonde H, Veltkamp JJ, Bieger R, Loeliger EA. Comparative study of the clinical effect of acenocoumarol and phenprocoumon in myocardial infarction and angina pectoris. Acta Med Scand 1971; 190: 535-540