COMPARISON OF A STANDARD AND A SENSITIVE THROMBOPLASTIN IN MONITORINGLOW-INTENSITY ORAL ANTICOAGULANT-THERAPY

The greater precision in prothrombin time monitoring obtained using th romboplastins with low international sensitivity index (ISI) values ar e believed to result in improved patient care. The authors conducted a blinded prospective study of 84 random patients on low-intensity warf arin therapy who were monitored with either a sensitive (ISI, 1.3) or standard (ISI, 1.9) thromboplastin. For the patients monitored with st andard and sensitive thromboplastins, respectively, no difference was found in the degree of anticoagulation (standard thromboplastin mean I NR, 2.4 vs. 2.5, P = .37; sensitive thromboplastin mean INR, 2.6 vs. 2 .6, P = .74; mean daily warfarin dose, 5.1 vs. 4.7 mg, P = .28) or eff icacy (warfarin dosage adjustments, 117 vs. 116; clinic visits, 362 vs . 378; percentage of therapeutic INR determinations, 47% vs. 48%). In addition, no difference was found in bleeding prevalence or severity ( .22 vs. .27 events per person-year observation). The authors concluded that monitoring anticoagulant therapy in the INR range of 2-3 with a standard thromboplastin may be comparable to monitoring with a more se nsitive thromboplastin with respect to efficacy, safety, and degree of anticoagulation achieved.