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* From the School of Pharmacy (Dr. Wittkowsky) and the Medical Center (Dr. Mullins), University of Washington, Seattle, WA; and the College of Pharmacy (Drs. Nutescu, Blackburn, Hardman, Mitchell, and Vats), University of Illinois at Chicago, Chicago IL.
Correspondence to: Edith A. Nutescu, PharmD, The University of Illinois at Chicago, College of Pharmacy, Department of Pharmacy Practice, 833 S Wood St, M/C 886, Chicago, IL; e-mail: enutescu{at}uic.edu
Abstract
Background: Anticoagulation management by a dedicated anticoagulation clinic improves patient outcomes compared to routine medical care. Telephone-based anticoagulation management has been described but has not been compared to management with traditional office-based visits. The objective of this study was to compare warfarin-related monitoring outcomes, clinical end points, and the use of health-care resources as a result of warfarin-related complications in anticoagulation clinic patients whose management was conducted by telephone or in-office-based visits.
Setting: Two university-affiliated anticoagulation clinics in Seattle, WA, and Chicago, IL.
Methods: A retrospective, observational cohort design was used to investigate anticoagulation clinic patients who were managed by telephone encounters compared to those managed during face-to-face in-office encounters.
Results: A total of 234 patients were evaluated; 117 patients managed by telephone were compared to 117 patients managed in office-based clinic visits. Monitoring outcomes (ie, time in therapeutic range and clinic visits per patient-year) were similar between groups. Differences in major bleeding (5.67% vs 5.62% per patient-year, respectively) and thromboembolic events (1.42% vs 2.81% per patient-year, respectively) between telephone-managed and face-to-face-managed patients did not reach statistical significance. The same was true for differences in the frequency of emergency department visits and hospital admissions to manage complications of warfarin therapy.
Conclusions: Telephone-based management of oral anticoagulation through a pharmacist-staffed anticoagulation clinic yielded clinical outcomes that were at least as favorable as those associated with traditional office-based visits. Telephone follow-up can be successfully used to manage warfarin therapy in patients who are unable to present in person to an anticoagulation clinic.
Key Words: anticoagulation • clinic management • outcomes • telephone management • warfarin
The safe and effective use of warfarin requires high-quality management to maintain patients within the appropriate therapeutic range.1 Proper monitoring requires routine international normalized ratio (INR) testing, appropriate dosing adjustments, active communication with patients, an appropriate treatment plan, and ongoing patient education.2 In the last decade, there has been a shift in oral anticoagulation therapy management from traditional physician-based settings to an anticoagulation clinic model staffed by pharmacists, nurses, or other nonphysician providers.3 Many studies45678 have shown that, in comparison to routine medical care, anticoagulation management through a pharmacist-staffed anticoagulation clinic is associated with improved patient outcomes, including lower rates of hemorrhage and recurrent thrombosis, as a result of more consistent monitoring, the early recognition of risk factors, and improved patient education.
Among numerous technological advances in medical care, the use of the telephone for health-care delivery has increased in scope and application.9 Effective telephone-based systems that are acceptable to patients as well as to health-care providers have been described for numerous therapeutic interventions, including the management of urinary tract infections in women, the monitoring of care and follow-up for depression, the management of diabetes, and smoking cessation, among many others.10111213
Telephone-based management of anticoagulant therapy has been described in several reports.141516 A survey of patients who were enrolled in a telephonic anticoagulation clinic found that these patients had a high degree of satisfaction with care and a high level of knowledge about warfarin therapy.17 One report18 described monitoring outcomes and clinical events in a telephone-based anticoagulation management service that were similar to previously reported outcomes in traditional office-based anticoagulation clinics. In addition, the results of a study8 of a centralized, telephonic, pharmacist-managed anticoagulation monitoring service showed that it reduced the risk of anticoagulation therapy-related complications compared to usual care. However, to our knowledge, no evaluation has compared the outcomes of patients managed by telephone vs by office appointment within an anticoagulation clinic setting. The purpose of this investigation was to evaluate warfarin-related monitoring outcomes, clinical end points, and the use of health-care resources as a result of warfarin-related complications in patients who were managed in an anticoagulation clinic setting either by telephone follow-up or via face-to-face office-based visits.
Materials and Methods
Setting
This research was conducted at two university-affiliated anticoagulation clinics. The Anticoagulation Clinic of the University of Washington Medical Center manages nearly 500 patients who are receiving warfarin therapy. The clinic is staffed by clinical pharmacists (1.5 full-time equivalent [FTE]) and an office assistant (1.0 FTE). Over 700 patient visits are conducted each month, 40% of which are in-office visits and 60% of which are conducted by telephone. INR results for office-based visits are determined using a rapid testing device (HEMOCHRON Jr. Signature Microcoagulation System; ITC; Edison, NJ) using blood samples obtained via venipuncture by hospital laboratory staff. Results are then transmitted in writing to the Anticoagulation Clinic prior to the patient’s subsequent clinic visit. INR results for patients managed by telephone are determined using standard laboratory methodology at local laboratories, with results called or faxed to the Anticoagulation Clinic. Patients are tracked using an internal computer database.
The Antithrombosis Clinic of the University of Illinois at Chicago Medical Center manages anticoagulation therapy for approximately 450 patients who are receiving therapy with warfarin. Clinical services and patient management is provided by clinical pharmacists (2.5 FTE), and support services are provided by a clinical technician (1 FTE). Approximately 650 patient visits are conducted each month, 75% of which are in-office visits and 25% of which are conducted by telephone. INR results for office-based visits are determined on site via a point-of-care testing device (ProTime; ITC) using whole-blood samples obtained via finger-stick. Immediately after the INR result is available, the patient is seen in the clinic by the clinical pharmacist. INR results for patients managed by telephone are determined using standard laboratory methodology at local laboratories, with the results called or faxed to the Antithrombosis Clinic. Patients are then contacted by the clinical pharmacist for telephonic management of their anticoagulation therapy. Patient data are tracked and documented by using an electronic medical record, which is the standard throughout the health system at the University of Illinois at Chicago.
Study Design and Patients
The medical and anticoagulation clinic records of patients who received warfarin therapy between the index dates of October 1996 and July 2003, and were managed by two university-affiliated anticoagulation clinics, were retrospectively reviewed to identify study participants. The study protocol was approved by the Investigational Review Board at each institution. Informed consent was waived due to the retrospective nature of the data collection.
The intervention group patients, whose anticoagulation therapy was managed by telephone, were receiving warfarin therapy for the primary or secondary prevention of embolic stroke, deep vein thrombosis, pulmonary embolism, or other arterial or venous thrombosis. Telephone-based management had been selected for these patients because they were unable to be seen in person due to physical disability, the inability to arrange or afford transportation, the fact that they lived a great distances from the clinic, or were unable to wait for a face-to-face visit and INR blood draws. The telephone-based interview followed the exact same structure and patient evaluation and education components as the in-clinic face-to-face patient interview. Control patients were patients whose anticoagulation management occurred during face-to-face office-based visits. All patients who were managed "exclusively" via telephone were included from each clinic in the intervention group (n = 117). The same number of control patients receiving face-to-face follow-up were then selected to match the same indications for anticoagulation therapy as those for the intervention group (n = 117). Data from the first 3 months of oral anticoagulant therapy for each patient were excluded. Over the course of the study period, patients in each group were excluded if they had more than two visits using the alternate management method.
Data Collection
A standardized data collection form was used at each center, and the data were collected by a single investigator at each center. Data elements extracted from the medical records for each patient included demographic characteristics, indication for warfarin therapy, goal INR, and duration of anticoagulation therapy. Anticoagulation clinic records provided evidence of the type of anticoagulation clinic visit (ie, phone vs office) and the INR values calculated at each encounter. At each clinic visit, patients were asked to report complications, including bleeding and thrombosis. These self-reported complications were confirmed by a review of objective diagnostic tests in the medical record and then documented in the anticoagulation clinic records. Patients were also asked to report emergency department visits and hospital admissions. These events were confirmed by a review of hospital and emergency department admissions records and of findings reported in the medical records, and subsequently were documented in the anticoagulation clinic records. During the review of medical records for this study, major bleeding events, which were defined as bleeding requiring hospital admission, and thromboembolic events were identified. Emergency department visits and hospital admissions specifically for complications of warfarin therapy were also identified. The sources of patient data for these outcomes included computerized medical records and anticoagulation clinic records.
Statistical Analysis
Statistical analyses of all variables were conducted using commercially available software (SPSS, version 13.0; SPSS Inc; Chicago, IL). To describe nominal data, frequencies or percentages were used. When testing for differences between intervention patients and control patients for nominal data, a 
2 test was employed. Interval or ratio scaled data were described using the mean, minimum, and maximum values, and the Student t test was used to compare differences between group mean values. A p value of < 0.05 was used to determine statistical significance. For nominally scaled variables, relative risk (RR) and corresponding 95% confidence intervals (CIs) were used to compare the relationships between both groups.
Results
A total of 234 patients, 117 in each management group, were included in the analysis and contributed 283.4 patient-years of data. Table 1 summarizes the demographic characteristics of the patients in each management group. The differences in sex, age, duration of therapy, indications for oral anticoagulation, and the number of patient-years of therapy contributed by patients in each group did not reach statistical significance.
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Telephone-based management of oral anticoagulation therapy has been described in several reports.814151618 To our knowledge, this is the first study to evaluate differences in monitoring outcomes, clinical end points, and health-care resource utilization between telephone-managed and office-managed patients within an anticoagulation clinic setting. The results showed no significant differences between the two groups, indicating that telephone-based follow-up was at least as effective as in-person visits to manage oral anticoagulation. It is important to highlight that the structure and complexity of our telephone-based interview and patient evaluation replicated the model of our in-clinic face-to-face visit. Therefore, our findings may not be generalizable to certain telephonic anticoagulation services that merely serve as databanks for screening out-of-range INR values and do not necessarily conduct a detailed patient evaluation.
The economic impact of using telephone-based management was not specifically investigated in this study. It has been shown previously19 that using a telephone-based approach for the follow-up of patients in a primary care clinic setting resulted in decreased costs as a result of the reduced utilization of medical resources, including clinic visits, hospital admissions, lengths of stay, and ICU days. Another study20 showed that one third of patients who succeeded in consulting a clinician by telephone would have otherwise gone to an emergency department. No formal pharmacoeconomic study has been conducted to evaluate the impact of telephone-based management. However, as telephone management is not reimbursed by most payers, anticoagulation clinics with a business model that requires a particular level of reimbursement may find that telephone management is not economically feasible.
Though patient perceptions of telephone-based follow-up were not specifically addressed in our study, several studies212223 in other therapeutic areas have shown that patients are highly satisfied with consulting their doctors by telephone as it reduces waiting periods, travel time, and travel costs, and may increase the frequency of contact. In one study24 assessing the role and value of a telephone-based follow-up program for the continuing care of 120 rheumatology outpatients, 90% of patients were satisfied with the discussion and advice given on the telephone, and 77% of patients rated the telephone program as being better than or equal to a clinic visit program. It also has been shown that telephone consultations are particularly valued by people living in rural areas and those whose health or social circumstances make visits to the hospital difficult.9
There were several limitations to this study that are typical of retrospective evaluations. Subjects were not randomly assigned to the telephone and clinic appointment groups, and thus group assignment may be impacted by selection bias. Patients in the telephone management group were allowed to be followed up in this manner because they were unable to come to the clinic for appointments. The reasons for the inability of these patients to come to the clinic (eg, physical disability, remote location, and transportation issues) may also have influenced treatment compliance, the stability of therapy, and clinical outcomes. Due to the relatively small number of patients included in each group, the study may lack adequate power to detect significant differences between the two groups. Time bias may also have influenced the results of this study. The staffing levels, the individual practitioners caring for patients, or other factors could have changed over the course of the study period. However, these issues are inherent in any anticoagulation clinic setting and thus would be expected to influence results regardless of the method of management.
Conclusion
No significant differences were found in INR control, number of major bleeding events, thromboembolic events, warfarin-related emergency department visits, or warfarin-related hospital admissions between patients whose oral anticoagulant therapy was managed by telephone compared to patients whose therapy was managed during face-to-face office encounters in an anticoagulation clinic setting. This study suggests the effectiveness of telephone-based anticoagulation management by an anticoagulation clinic for patients who are unable to come to the clinic due to personal preference, distance, transportation, or disability issues. These findings may not be applicable to telephone-based INR screening services that lack a detailed program for patient evaluation and education.
Footnotes
Abbreviations: CI = confidence interval; FTE = full-time equivalent; INR = international normalized ratio; RR = relative risk
The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
Received for publication January 29, 2006. Accepted for publication April 25, 2006.
References
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