Abstract 18820: Estimating Time In Therapeutic Range Using The Percentage of Visits in International Normalized Ratio Range Among Patients with Nonvalvular Atrial Fibrillation

Abstract

OBJECTIVES: Time in therapeutic range (TTR) has been a quality indicator for level of anticoagulation even though it is not readily available for practitioners to estimate level of anticoagulation for patients. A simpler measure that is based on the number of visits, percentage of visits in international normalized ratio (INR) range (PVIR), may estimate the anticoagulant control. This measure is examined for correlation with TTR levels achieved among patients with nonvalvular atrial fibrillation (NVAF) in a large retrospective database.

METHODS: We analyzed longitudinal patient-level anticoagulation management records collected between 2006 and 2010 by decision support software, CoagClinic™. Adult patients with NVAF with at least 2 anticoagulation clinic visits and no gap >180 days between visits were identified. The Rosendaal method was used to calculate TTR. Anticoagulation visits with 2.0≤ INR≤3.0 was defined as visits within INR range. PVIR was calculated by dividing the number of visits within INR range by the total number of visits. PVIR was stratified by the increment of 10%, and then compared to corresponding TTR. Pearson correlation coefficient between TTR and PVIR was calculated.

RESULTS: We identified 36,978 patients who met all inclusion criteria. The mean (±SD) age was 72.3±10.6 years, with 78.4% ≥65 years. The mean (±SD) TTR was 62.2±20.7. On average, patients had 39 visits, of which 23 were in INR range. The average PVIR was 59%. A substantial proportion of patients (79%) had PVIR ≤70%; 18% of patients had PVIR between ≤71% and ≤90%; only about 3% had PVIR ≥91%. PVIR and TTR showed a strong linear relationship (Table 1; Pearson correlation coefficient=0.87).

CONCLUSIONS: Percentage of visits in INR range (PVIR) offers a simplified measure for daily practitioners to estimate level of anticoagulation control and help identify patients with poor control.