Willingness to pay for avoiding coronary restenosis and repeat revascularization: results from a contingent valuation study

Abstract

Background: Despite technological improvements, percutaneous coronary intervention (PCI) remains limited by restenosis requiring further revascularization procedures during the ensuing year. New technologies aiming to reduce restenosis are expensive and may increase net healthcare costs. Economic evaluations of such therapies have been performed, but have been hindered by the need to assess the disutility of short-term health care events and repeat coronary revascularization as well as the lack of benchmark standards for intermediate health outcomes. The contingent valuation approach may offer particular advantages when evaluating treatments that improve short-term health outcomes. Objective: To examine patients’ willingness to pay (WTP) for treatments that may reduce the risk of restenosis and repeat revascularization after PCI. Methods: We used a contingent valuation approach to evaluate WTP among participants in two large clinical trials evaluating new PCI devices. The baseline scenario described a 30% probability of repeat revascularization following the initial procedure. Patients were asked to indicate, using a close-ended (referendum) question, their out of pocket WTP for an improved treatment that would reduce this risk. Three different prices ($ 500, $ 1000, and $ 1500) and three levels of absolute risk reduction (10, 20, and 30%) were randomly varied creating nine sub-samples of patients. Patients’ responses were analyzed using both parametric and non-parametric methods. Results: 1642 patients completed the WTP question. The WTP medians for the 10 and 20% risk reductions were $ 273 and $ 366, respectively; the median WTP for the 30% risk reduction was significantly higher at $ 1162 (P<0.001). Higher household income (OR=1.57, P<0.001) was independently associated with a higher WTP. Conclusions: Although short-lived, avoidance of coronary restenosis may have considerable value to patients undergoing percutaneous coronary interventions. These findings may have important implications for emerging technologies such as drug-eluting stents.

Introduction

Coronary atherosclerosis is the major cause of death and disability in Western countries. Consequently, coronary revascularization procedures are among the most frequent and costly procedures performed within the United States healthcare system today. In recent years, the use of percutaneous coronary interventions (PCI) has increased to approximately 700,000 procedures per year in the United States alone [1]. Despite ongoing technologic advances, PCI remains limited by restenosis (re-narrowing) of the treated artery that may ultimately result in recurrent myocardial ischemia and anginal symptoms necessitating one or more repeat revascularization procedures. Over the past decade, coronary stenting (placement of a metallic mesh prosthesis in the artery at the time of PCI) has been shown to reduce the rates of angiographic and clinical restenosis compared with conventional balloon angioplasty [2], [3], [4], [5]. As a result, stenting is currently performed in ∼80% of all coronary interventions in the United States [6], [7]. Despite the improved outcomes seen with stenting, percutaneous treatment of CAD is still hampered by a 20–30% incidence of restenosis [8], with substantial clinical and economic consequences. Thus, there is considerable impetus for the development of novel therapeutic strategies to limit the occurrence of restenosis after coronary stenting.

Recently, several technologies including coronary brachytherapy [9] and drug-eluting coronary stents [10], [11], [12] have been shown to further reduce rates of restenosis and repeat revascularization compared with conventional therapy, but these advances come at a price. Formal economic evaluations of both stents and brachytherapy have demonstrated that neither of these techniques generates sufficient downstream cost savings to fully offset the higher up-front costs of these therapies [13]. Thus, economic evaluations must consider whether the benefits of such therapies (in terms of reduced rates of recurrent symptoms and repeat revascularization procedures) are worth the additional costs [14].

The standard approach to address this question is cost-utility analysis, in which the benefit is measured in terms of quality-adjusted life years (QALYs) [15]. Although the use of QALYs as an outcome measure is theoretically valid, several pragmatic issues limit the attractiveness of this endpoint for valuing treatments aimed at avoiding restenosis and repeat revascularization after PCI. Since there is no evidence that coronary restenosis affects short-term or long-term survival after PCI [16], one would not expect treatments whose sole benefit is a reduction in restenosis to improve population-level life expectancy. On the other hand, there is fairly consistent evidence that coronary restenosis has an important, albeit transient, impact on health-related quality of life [3], [17], [18]. Therefore, a treatment that results in a lower rate of restenosis would be expected to improve a patient’s quality of life, and any assessment of the cost-effectiveness of such a treatment must depend critically on the utility weight assigned to the restenosis health state.

On a practical level, obtaining a valid assessment of the disutility associated with coronary restenosis poses certain methodological challenges. While restenosis and its attendant symptoms may persist for weeks or months in some healthcare systems, in the US patients with restenosis rarely wait more than 1–2 weeks after the onset of symptoms before undergoing repeat revascularization. Thus, capturing patients at the nadir of their symptomatic state is quite challenging in practice. As an alternative, one might consider an attempt to assess utility over a longer time window so as to integrate the effects of the restenosis process over an extended period. It is unclear, however, whether patients can truly integrate such transient events into longer term assessments of preference. Given these limitations, it has been common for economic evaluations of treatments that reduce restenosis to be presented in terms of cost per repeat revascularization avoided [5], [19], [20], [21]. While this metric is straightforward to assess, interpretation of such studies is hampered by a lack of benchmarks for this outcome.

An alternative approach to valuing health outcomes that may offer particular advantages when evaluating treatments that improve short-term health outcomes is the contingent valuation (i.e., “willingness to pay”) approach [22]. In contrast to the QALY methodology used in cost-utility analysis, in which the benefit is based on preferences for health outcomes only, the willingness to pay (WTP) method imposes no restrictions on which attributes of a program may be considered in its valuation [23], [24]. Consequently, the WTP approach captures the opportunity cost of a certain health benefit by measuring directly what individuals are willing to forgo to enjoy a particular benefit.

Although this method has been applied to a broad range of medical interventions [23], [25], [26], [27] including patients with angina pectoris [28], it has not previously been applied to techniques in interventional cardiology. We therefore sought to evaluate WTP for treatments that reduce coronary restenosis and repeat revascularization, using a population of patients undergoing percutaneous coronary intervention in the setting of two large-scale randomized clinical trials.