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Predictors of Healthcare Costs After Initiating Dabigatran Versus Warfarin

The study found no mean difference in all-cause healthcare costs for patients with newly diagnosed nonvalvular atrial fibrillation initiating treatment with dabigatran versus warfarin.
Published Online: Feb 02,2018
Sabyasachi Ghosh, MS; Jason P. Swindle, PhD, MPH; John C. White, DPM, MS; Stephen D. Sander, PharmD; Cheng Wang, MD, PhD

Objectives: To estimate the 1-year stroke-related cost to manage ischemic stroke (IS) and hemorrhagic stroke (HS) events in a population with atrial fibrillation (AF).
Study Design: Retrospective database analysis and economic model.
Methods: An incidence-based model was developed using published AF prevalence rates and stroke incidence/mortality rates observed in the MarketScan databases (2005-2011). Adult patients who had ≥1 inpatient or ≥2 outpatient claims for AF and ≥1 primary inpatient claim for stroke were analyzed. Adjusted mean costs for IS and HS index event hospitalizations and follow-up care during the 1 year following index stroke event were estimated using generalized linear models controlling for potential confounding variables.
Results: In a health plan with 1 million enrollees, we estimated 9500 patients with AF. Annual stroke incidence rates among patients with AF ranged from 0.23-3.57 (IS) and 0.06-0.49 (HS) per 100 person-years. Mortality rates during IS and HS hospitalizations were 5.6% and 23.2%, respectively. Adjusted mean cost for patients who died during hospitalization was higher for IS than HS ($29,810 vs $23,492; P <.0001), although adjusted mean 1-year cost associated with IS was lower than with HS among those who survived ($25,635 vs $48,850; P <.0001). Total annual stroke-related healthcare costs for the health plan were estimated to be $4,930,787, with 74% of costs attributable to IS.
Conclusions: Among patients with AF, IS accounts for more annual healthcare costs to a health plan due to its higher incidence than HS. This study provides data to inform future risk-benefit analyses of anticoagulation therapy for stroke prevention in patients with AF from a population perspective.

                                                                                         Am J Pharm Benefits. 2018;10(1)22-30

Atrial fibrillation (AF) confers a 4- to 5-fold higher risk of stroke, resulting in great morbidity and substantial healthcare costs.1-3 Oral anticoagulant (OAC) therapy is recommended to reduce risk of stroke among patients with AF at moderate-to-high risk of stroke.4,5 Warfarin has historically been the mainstay of OAC therapy. However, since 2010, therapeutic options have expanded with the introduction of dabigatran6 and other novel OACs indicated for nonvalvular AF (NVAF).7 In the Randomized Evaluation of Long-Term Anticoagulant Therapy clinical trial, dabigatran was associated with lower rates of stroke and systemic embolism compared with dose-adjusted warfarin.8

Real-world economic comparisons of dabigatran and warfarin among patients with NVAF initiating OAC therapy have recently been conducted. These retrospective claims analyses of all-cause healthcare costs suggest that dabigatran is cost-neutral relative to warfarin.9-12 In these studies, costs were reported for overall patient samples13 and did not examine whether subgroups of patients with similar demographic/clinical profiles might incur different costs when initiated on dabigatran versus warfarin.

Clinical characteristics, including disease severity, have been studied widely as risk factors that, when adjusted for, enable more accurate assessment of healthcare costs. The importance of incorporating patient heterogeneity into economic evaluations is also recognized.14 Patients with AF are a clinically heterogeneous population5,13 and initiation on appropriate OAC therapy has the potential to improve clinical outcomes and reduce resource use and costs. The Affordable Care Act, which reimburses services based on clinical episodes, rather than on a fee-for-service basis,15 has created opportunity to explore the episode-based approach for examining differences in costs among patients with different comorbidities undergoing treatment for their conditions. One such approach is Episode Treatment Group (ETG), a condition classification methodology that defines episodes of care for measurement of associated healthcare costs.16 ETG methodology has been vetted in actuarial science17-19 and in health economics and outcomes research.20 Episode Risk Group (ERG) is a medically meaningful metric to account for patient heterogeneity, which assesses risks of incurring costs according to comorbidities and medical complications.16

Given the gap in current literature regarding subgroups of real-world patients with NVAF who may incur different healthcare costs following initiation of dabigatran versus warfarin, we conducted exploratory modeling to assess whether ERG risk score and other patient characteristics were predictive of differential all-cause healthcare costs computed on an episode basis using ETG methodology among these 2 cohorts. We also examined traditional predictors of costs, namely patient demographics and Charlson Comorbidity Index (CCI) score, using a non–episode-based approach.