Effect of Apixaban Versus Warfarin Use on Health Care Resource Utilization and Costs Among Elderly Patients with Nonvalvular Atrial Fibrillation.

Abstract

The clinical trial ARISTOTLE showed that apixaban was superior to warfarin in reducing the risks of stroke and bleeding among patients with nonvalvular atrial fibrillation (NVAF). Further study of the effect of apixaban versus warfarin use on health care resource utilization (HCRU) and associated costs in the real-world setting is warranted, especially among elderly patients who are at higher risk of stroke and bleeding. To compare HCRU and costs among elderly NVAF patients treated with apixaban versus warfarin in the United States. Elderly patients (aged ≥ 65 years) with Medicare coverage who initiated apixaban or warfarin were identified from the Humana research database during January 1, 2013-September 30, 2015. Patients were required to have 12 months of continuous insurance coverage before drug initiation (baseline period) and an atrial fibrillation diagnosis during the baseline period or on the date of drug initiation. NVAF patients were grouped into cohorts depending on the drug initiated. Propensity score matching (PSM) was conducted to control for differences in demographics and clinical characteristics of study cohorts. Patients were followed after the index date for a variable length of follow-up. All-cause and disease-specific HCRU and costs during the follow-up were evaluated before and after PSM and reported as per patient per year. Of the overall (unmatched) population, 8,250 patients (mean age: 78.0 years) initiated apixaban and 14,051 patients (mean age: 78.2 years) initiated warfarin. Among NVAF patients who initiated apixaban versus those who initiated warfarin, mean Charlson Comorbidity Index (CCI) scores (3.0 vs. 3.4, P < 0.001); stroke risk scores, including CHADS2 (2.7 vs. 2.9, P < 0.001) and CHA2DS2-VASc (4.6 vs. 4.7, P < 0.001); and bleeding risk scores, including HAS-BLED (3.1 vs. 3.2, P < 0.001), were lower. Additionally, total annual all-cause health care costs were lower during the baseline period for patients treated with apixaban versus warfarin ($17,077 vs. $20,236, P < 0.001). After PSM, 14,214 patients were matched, with 7,107 in each cohort. Mean age, CCI score, and stroke and bleeding risks were similar between matched cohorts, as were total all-cause health care costs during the baseline period. During the follow-up among matched cohorts, apixaban versus warfarin treatment was associated with higher annual pharmacy costs ($5,159 vs. $2,867, P < 0.001) but lower annual inpatient ($8,327 vs. $14,296, P < 0.001), outpatient ($9,655 vs. $11,469, P < 0.001), and total all-cause health care costs ($23,141 vs. $28,633, P < 0.001), which were reflective of lower inpatient, outpatient, and all-cause HCRU among apixaban-treated patients. Furthermore, bleeding-related ($2,101 vs. $3,963, P < 0.001) and stroke-related ($652 vs. $1,178, P = 0.001) annual medical costs were lower for patients treated with apixaban versus warfarin. After controlling for differences in patient characteristics, in the real-world setting apixaban versus warfarin use was associated with less HCRU and lower total all-cause health care costs and costs for bleeding- and stroke-related medical services, but greater pharmacy costs, among elderly NVAF patients. This study was sponsored by Pfizer and Bristol-Myers Squibb. Deitelzweig is a consultant for Pfizer and Bristol-Myers Squibb and has served on their advisory boards and received speaker fees. Deitelzweig also serves as consultant and advisory board member to Portola and Janssen. Luo, Trocio, and Mardekian are employees of Pfizer and own stock in the company. Gupta and Curtice are employees of Bristol-Myers Squibb and own stock in the company. Lingohr-Smith, Menges, and Lin are employees of Novosys Health, which received research funds from Pfizer and Bristol-Myers Squibb to conduct this study and develop the manuscript. Study concept and design were primarily contributed by Deitelzweig, Luo, and Gupta, along with Trocio, Mardekian, Curtice, and Lin. Lin, Menges, and Lingohr-Smith took the lead in data collection, with assistance from the other authors. Data interpretation was performed by Deitelzweig, Menges, and Lin, with assistance from the other authors. The manuscript was written by Lingohr-Smith and Menges, along with the other authors, and revised by all the authors. Some aspects of this study were presented at the American Heart Association Scientific Sessions in New Orleans, Louisiana, November 12-16, 2016.