THROMBOTIC EVENTS DURING ORAL ANTICOAGULANT TREATMENT - RESULTS OF THE INCEPTION-COHORT, PROSPECTIVE, COLLABORATIVE ISCOAT STUDY

The paper reports on rate and type of thrombotic events occurring duri ng the observational, prospective, inception-cohort, multicenter ISCOA T study. 2,745 unselected, daily practice patients, consecutively refe rring to 34 Italian anticoagulation clinics to monitor the oral antico agulant treatment, were included in the study from beginning of their first anticoagulant course. During a total follow-up of 2,011 patient- years of treatment 70 thrombotic events (3.5 per 100 patient years) we re recorded in 67 patients: 20 fatal (1%), 39 major (1.9%) and 11 mino r (0.6%). 34/70 events occurred within the first 90 days of treatment (relative risk - at multivariate analysis - of less than or equal to 9 0 days vs. >90 = 20.6, C.I. 12.7-33.5; p <0.0001). The risk was higher in patients aged greater than or equal to 70 y (1.62, C.I. 1.0-2.61; p <0.05), and when indication for anticoagulant treatment was peripher al/cerebral arterial disease (1.84, C.I. 1.01-3.36; p <0.05). The freq uency of thrombotic events was 17.5% when international normalised rat io (INR) levels were <1.5, decreasing to 2.3% for INRs within the 2-2. 99 category (relative risk of INRs <2.0 vs. greater than or equal to 2 = 1.88, C.I. 1.16-3.07; p<0.05). The recorded rate of thrombotic even ts was lower than that reported in the few available studies. A greate r risk should be expected during the first 90 days of treatment, when anticoagulation levels are <2.0 INR, in patients > 70 years and in tho se with cerebrovascular/peripheral arterial disease.