ASSESSMENT OF THERAPEUTIC QUALITY-CONTROL IN A LONG-TERM ANTICOAGULANT TRIAL IN POSTMYOCARDIAL INFARCTION PATIENTS

Various methods have been described to evaluate efficacy of anticoagul ant therapy using the international normalized ration (INR). We compar ed the following approaches: (1) total INR's or the most recent measur ement; (2) percent rime within therapeutic range, with INR changing di rectly or halfway between visits; and (3) total observation time assum ing INR changing linearly. The study population comprised 1700 post my ocardial 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. Therapeuti c 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. Ou r findings call for an urgent improvement of standard of anticoagulant control in the first months following commencement of treatment.