Studies demonstrate the effectiveness of anticoagulation management service (AMS) in providing antithrombotic therapy for eligible patients. We sought to extend this concept by determining whether an interim telephone model (IT) is comparable to our current AMS model at achieving optimal therapeutic outcomes.
The 36-month trial (24-month study plus 12-month extension) enrolled 192 eligible patients receiving long-term warfarin therapy at a Veterans Affairs hospital. Consenting participants were randomly assigned to either our current face-to-face clinic model (AMS), or our IT model. The primary outcome was the percentage of time individuals' international normalized ratios (INRs) were maintained within their target INR range (2.0-3.0 or 2.5-3.5). Secondary outcomes included the number of adverse events (eg, thromboembolism or hemorrhage) experienced during the study.
We found no statistically significant difference between the 2 groups in the percentage of time maintained within INR target range overall (55.1% for AMS; 57.8% for IT; P = .28) nor over the course of the study. There were no statistically significant differences in the rate of thromboembolic or serious bleeding events between IT and AMS participants. Nevertheless, we did note differences related to intensity of anticoagulation. The IT group receiving treatment at a higher intensity (INR, 2.5-3.5) experienced greater anticoagulation control (P = .04) and fewer complications than the AMS group. The IT participants, however, reported a significantly higher rate of minor bleeding events, experienced mainly by those at an INR range of 2.0 to 3.0.
Our IT model is a viable modification of our AMS model for the management of patients undergoing chronic anticoagulant therapy.