ArticlesBleeding complications of oral anticoagulant treatment: an inception-cohort, prospective collaborative study (ISCOAT)
Introduction
Oral anticoagulant therapy is increasingly used for the prevention and treatment of thromboembolic complications of vascular disease.1 Bleeding is the most important complication. In a review of observational studies,2 average annual rates of fatal, major, and major/minor bleeding were 0·8, 4·9, and 15%, respectively. In another review,3 bleeding rates ranged from 0 to 4·8% for fatal bleeding and from 2·4 to 8·1% for major bleeding. Reliable data are lacking on the true frequency of complications in patients on oral anticoagulants because of methodological limitations.4 Many studies were done before the introduction of the international normalised ratio system (INR) for prothrombin time (PT),5, 6 or calculated INR retrospectively. Most studies that used the INR system were in highly selected patients. The few observational studies were either retrospective or descriptive, and were not in a clearly defined inception cohort (ie, followed up in one clinic from start of treatment).4, 7 Observational studies that included an inception cohort were retrospective and did not use INR8 or selected patients.9
We have prospectively assessed the rate of bleeding complications in outpatients monitored from the beginning of oral anticoagulation.
Section snippets
Centres
This study was done in thirty-four centres of the Italian Federation of Anticoagulation Clinics. Each centre is required to: give extensive instructions to all new patients enrolled; follow-up patients by INR; fix the date for next visit and meanwhile prescribe daily anticoagulant dose; monitor changes in patients' habits, diet, and co-medication, illnesses, bleeding complications and scheduled surgical or invasive procedures; and take part in external laboratory quality-control.
Design and patients
This was an
Results
2745 patients (43% female) were included (table 1). Twenty-five centres enrolled under 100 cases, and nine enrolled over 100. In the centres that enrolled over 100 patients, the number of anticoagulated patients not included in the study (second anticoagulation course, anticoagulation started after 30 days, geographic inacccessibility) ranged from 6 to 11 % of the patients included. The anticoagulant drug used was warfarin in 1752 (63·8%) and acenocoumarol in the remaining 993 (36·2%) patients.
Discussion
We were able to estimate haemorrhagic risk complications during oral anticoagulation in outpatients monitored by INR in specialist anticoagulation clinics. The results reflect the normal practice of Italian centres. The rate of fatal, major, and minor bleeding events was 0·25, 1·1, and 6·2 per 100 patient-years of follow-up, respectively. These figures are lower than the average annual frequencies of bleeding (0·8, 4·9, and 15 per 100 patient-years for fatal, major, and major/minor bleeding,
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