In this proof-of-concept study, we evaluated the addition of an interactive voice response system to a computerized decision support system to facilitate the management of oral anticoagulation therapy in patients whose anticoagulation control was already stable. Anticoagulation control was similar with and without the interactive voice response system. Most of the patients were satisfied with the system. The system was effective in communicating complex information, as indicated by the high rate of successful delivery of messages (77.8%) without input from staff. Importantly, the interactive voice response system reduced the workload of clinic staff by 33%. However, these results may have limited generalizability to unselected patients.
Anticoagulation control in our patient population was exceptionally good at baseline. In a systematic review35
of studies evaluating anticoagulation control, we found that the average time within the therapeutic range was 56.7% in community settings and 65.6% in anticoagulation clinics. In contrast, the patients in this study spent 79.9% of the time within the therapeutic range before the intervention, which made it very unlikely that the intervention would result in a significant improvement. Nonetheless, it was reassuring that anticoagulation control did not decrease during the intervention. In addition, the interactive voice response system required less work from staff members.
The absence of any hemorrhagic or thromboembolic events in our cohort might be considered notable. However, we feel that this result was unsurprising, for 3 reasons. First, we followed a relatively small number of patients for a short period of time (a total of 135.0 patient-years of observation). Given the overall risk of adverse events of 15% per year, it is possible that very few, if any, events would have occurred in our cohort simply by chance. Second, patients were within the therapeutic range close to 80% of the time during the study. Because the risk of adverse events is minimized when the international normalized ratio is within therapeutic range, the expected risk of events was low. Third, the patients in our cohort were younger and healthier than patients evaluated in previous studies. As age and comorbidity are strong predictors of the risk of bleeding, our study might have been biased toward a low rate of adverse events.
A previous evaluation of an interactive voice response system used in managing oral anticoagulation therapy36
was limited because it did not measure anticoagulation control or structural indicators. Also, the system in the earlier study was not integrated with a computerized decision support system and was therefore more cumbersome to use. The interactive voice response system in our study was easy to use and could be implemented by large health management organizations. This decision support tool would be even more efficient if the computerized decision support system were integrated with a laboratory information system, so as to make manual data entry unnecessary.
Strengths and limitations
Our study had important strengths. First, we had perfect follow-up of our study population. All patients completed the post-study interview. In addition, once the study was complete, most chose to continue using the interactive voice response system rather than reverting to the standard monitoring system. Furthermore, the follow-up period for each patient was adequate to accurately assess anticoagulation control. Although the total observation time for the intervention period was 22 years longer than that for the pre-intervention period, we believe that the 2 periods were sufficiently long to justify our comparisons. Second, we selected our study population using clinically relevant, transparent eligibility criteria. These criteria yielded a clear inception cohort. In addition, a high proportion of the patients whom we approached agreed to participate, which indicates that the study population was highly representative of the clinic’s population. Third, our range of relevant, objective indicators provided a comprehensive assessment of the interactive voice response system.
Our study also had limitations. First, the study population consisted of a highly selected group of users of oral anticoagulants. Most of the patients monitored by the anticoagulation clinic had stable anticoagulation control and were therefore not representative of most community-based patients.35
Second, we were unable to determine the true utility of the interactive voice response system because our study lacked a concurrent control. The results of this pretest–posttest study suggested that care with the interactive voice response system may be noninferior. However, the limited statistical power of the study and the lack of a randomized design prevented us from conclusively demonstrating noninferiority. A randomized controlled trial would be required to obtain more robust evidence.
We have demonstrated that interactive voice response systems have a potential role in improving the monitoring of patients who are taking oral anticoagulants. Future randomized studies will be required to conclusively demonstrate the effectiveness of this technology. Such studies should also be based on a more representative sample of users of oral anticoagulants. Given our experiences, we also recommend that this type of decision support tool be considered for management of other high-risk medication therapies for which laboratory monitoring is required.