Efficacy and Safety Outcomes for Patients Taking Warfarin Who Were Switched From Face-to-Face to Telephone Anticoagulation Clinic

Study Endpoints

The primary endpoints of the study included TTR, defined as the percentage of anticoagulation visits at which the INR values were in the patient-specific therapeutic range ± 0.2 (excluding any subtherapeutic INR values within 2 weeks after planned short-term discontinuation of warfarin), event rate of cerebral vascular accidents (CVA)/transient ischemic attacks (TIA) and venous thromboembolism (VTE), and event rate of major bleeds. Major bleeds were defined as any fatal bleed, a symptomatic bleed in a critical area or organ (intracranial, intraspinal, intraocular, retroperitoneal, intraarticular or pericardial or intramuscular with compartment syndrome), a fall in hemoglobin (Hg) ≥ 2 g/dL, or requiring transfusion of ≥ 2 units of whole blood or packed red blood cells.

Secondary endpoints of the study included event rate of minor bleeds (defined as any bleed not defined as a major bleed); time between follow-up appointments; number of acute care visits, emergency department (ED) visits, or hospitalizations due to anticoagulation; time to follow-up after hospital discharge, ED visit or acute care visit due to anticoagulation (if applicable); number of critical INRs as defined by local policy (INRs ≥ 5); number of canceled or no-show appointments; and compliance with monitoring of liver function test (LFT) and complete blood count (CBC) every 6 months per local policy.

Data Collection

To arrive at study endpoints, data collection included (1) demographics: age, ethnicity, and gender; (2) laboratory values: albumin, CBC, INR, LFT, and thyroid-stimulating hormone (TSH); (3) warfarin information: chart-documented adherence, dose and schedule, fill history, indication, INR goal per chart documentation, and reason for sub- or supratherapeutic INR; (4) safety: CVA/TIA, VTE, major bleeds, minor bleeds, and hospitalization/ED visits/acute care visits; (5) comorbid conditions: alcohol use, anemia, atrial fibrillation (AF), atrial flutter, cancer, coagulation deficiencies, congestive heart failure (CHF), diabetes mellitus (DM), hemodialysis, history of bleed, hypertension, liver cirrhosis, peptic ulcer disease, peripheral vascular disease, previous VTE, previous CVA/TIA, and valve replacement; (6) concomitant medications: aspirin, aspirin/extended-release dipyridamole, clopidogrel, dalteparin, enoxaparin, fondaparinux, nonsteroidal anti-inflammatory drugs (NSAIDs), unfractionated heparin, and warfarin; and (7) appointment data: time between appointments; time to follow-up after hospital discharge, ED visit or acute care visit (if applicable); and number of canceled or no-show appointments. Patient data were collected for 24 months total: the 12 months immediately before switching to telephone anticoagulation clinic (while the patient was followed in the face-to-face anticoagulation clinic) and the 12 months immediately after switching to telephone anticoagulation clinic.

Statistical tests used in this study included paired t test and Fisher exact test. P < .05 was determined to be statistically significant.

Results

A total of 156 patient charts were reviewed. Ninety-five patients were excluded, and 61 patients were included (Figure 1). Patients were excluded because they were either not enrolled in a face-to-face clinic for 1 continuous year prior to the switch or not enrolled in a telephone clinic for 1 continuous year after the switch. Patients also were excluded if they alternated between a face-to-face and telephone clinic and did not have at least 70% of their anticoagulation visits at the face-to-face clinic before the switch or at least 70% of their anticoagulation visits with the telephone clinic after the switch.

Baseline Characteristics

The study population was predominantly male with a mean age of 67 years. Most of the patients were African American. The most common indications for anticoagulation included AF, atrial flutter, previous VTE, or multiple indications. The most common INR goal range for patients was 2 to 3. The most common comorbid conditions were hypertension, alcohol use, CHF, and DM. Concomitant medications were noted if they were used anytime during the observation period; the most common were aspirin, NSAIDs, enoxaparin and dalteparin (Table 1).

Endpoints

There was not a statistically significant difference between the average TTR for patients for the face-to-face and telephone groups (Table 2). More than 85% of patients had a similar TTR between the groups or were in TTR more often during telephone clinic vs face-to-face clinic (Figure 2). One patient had a CVA during the face-to-face clinic period, and another patient had a TIA during the telephone anticoagulation clinic period. No VTE events were reported in either group. Further, there was 1 major bleed in the face-to-face clinic period (asymptomatic Hg drop ≥ 2 g/dL) and 3 major bleeds (asymptomatic Hg drop ≥ 2 g/dL, intraocular bleed, and gastrointestinal bleed) in the telephone clinic period, but this difference also was not statistically significant.

There were no statistically significant differences for any of the secondary endpoints except for compliance with LFT monitoring, which was higher in the telephone clinic. There were 22 minor bleeds found during face-to-face anticoagulation clinic and 19 minor bleeds found during telephone anticoagulation clinic. The most common types of minor bleed for both clinic settings were bruising at injection site (while using low molecular-weight heparin) and epistaxis.

There were 2 additional endpoints in the study for telephone clinic patients to assess time spent on telephone visits and ability to reach the patient by phone if they had laboratory tests drawn. In the telephone clinic, patients with completed labs were unreachable 2.1% of the time. The average amount of time spent on telephone visits was 8.0 (± 0.89) minutes.