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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

Objective: To identify patient characteristics predictive of all-cause healthcare costs among individuals with newly diagnosed non-valvular atrial fibrillation (NVAF) who initiated oral anticoagulant therapy with dabigatran or warfarin. 

Study Design: Retrospective analysis of administrative claims data of patients with newly diagnosed NVAF. 

Methods: Dabigatran and warfarin cohorts were identified by first claim (index date) during 10/1/2010 to 11/30/2012. Episode-based costs (all-cause) were determined using Episode Treatment Group (ETG) methodology and computed as per-patient-per-month. Baseline predictors of cost included baseline characteristics and baseline Episode Risk Group (ERG) risk score, which was grouped into 6 categories. To assess cohort differences in subgroups of patients, predictor variables representing the interaction of treatment cohort with patient characteristics were of primary interest. Cost ratios were then computed for subgroups of patients with different characteristics. 

Results: Cohorts included 4150 dabigatran- and 11,032 warfarin-treated patients. Compared with warfarin, dabigatran patients were younger (mean age: 67.3 vs. 72.5 years; P<0.001) and had lower mean ERG risk scores (4.1 vs. 5.6, P<0.001). Treatment cohort was not a statistically significant predictor of costs. Compared with warfarin, dabigatran was associated with higher cost at ERG risk scores of 2.1 to 4.0 and lower cost at scores of 6.1 to 8.0. 

Conclusions: Adding to existing evidence that treatment with dabigatran (vs warfarin) for NVAF would not incur higher all-cause healthcare costs, this study found that differences in all-cause healthcare costs did not follow a trend across subgroups of patients with NVAF based on different ERG risk score categories, favoring either therapy.

                                                                                         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.