Willingness-to-pay and parametric trends in cost-effectiveness and cost-utility studies in ophthalmology

Abstract

Objective

To evaluate the frequencies of input parameters in cost-effectiveness analyses (CEA) within ophthalmology, particularly in willingness-to-pay (WTP), and to assess trends over time in studies conducted in the United States.

Methods and analysis

A cross-sectional analysis of CEAs from the Tufts Medical Center CEA Registry spanning 1993 to 2022 was conducted, including all studies evaluating diseases of the eye and adnexa. The primary outcomes measured included trends in WTP thresholds, funding sources, types of interventions and disease classifications.

Results

A total of 82 US-based CEAs met the inclusion criteria. All studies assessed outcomes in quality-adjusted life years (QALYs). WTP thresholds of US$50 000 (41%) and US$100 000 (39%) were most frequently reported, with US$150 000 emerging in 9% of studies since 2019. Discounting at 3.0% for costs and QALYs was universally applied. Government (33%), nonprofit (29%) and pharmaceutical (17%) funding predominated. Pharmaceutical-funded studies often employed higher WTP thresholds of US$100 000 (29%) and US$150 000 (29%). The most common intervention types were surgical (40%) and pharmaceutical (40%), whereas diseases of the choroid and retina (43%) were most frequently studied. Healthcare perspectives (17 studies) were more commonly reported than societal perspectives (6 studies).

Conclusions

US-based ophthalmology CEAs commonly use US$50 000–$100 000 WTP thresholds and a 3.0% discount rate, with higher thresholds emerging recently. Public and nonprofit funding predominates, focusing on retinal diseases and surgical or pharmaceutical interventions. Reassessing fixed WTP thresholds and incorporating societal perspectives could improve CEAs’ relevance, ensuring alignment with evolving economic and healthcare landscapes.

WHAT IS ALREADY KNOWN ON THIS TOPIC

• US ophthalmology cost-effectiveness analyses often use outdated willingness-to-pay (WTP) thresholds of US$50 000 and US$100 000, despite economic shifts and rising healthcare costs.

WHAT THIS STUDY ADDS

• This study shows the continued use of these thresholds, with a growing trend towards $150 000 in recent years, especially in pharmaceutical-funded studies.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

• Findings support the need for updated, flexible WTP thresholds to better reflect current economic conditions and improve decision-making in health policy.

Introduction

Cost-effectiveness analyses (CEA) and cost-utility analyses (CUA) are essential tools for informing healthcare decision-making, providing insight into the value of medical interventions relative to their costs.¹ Central to these analyses are input parameters such as willingness-to-pay (WTP) thresholds, discount rates and measures of effectiveness. WTP thresholds represent the maximum amount a society is willing to pay for a unit of health benefit, typically expressed as a quality-adjusted life year (QALY) gained.² Despite the widespread use of WTP thresholds in CEAs, commonly cited values of US$50 000 and US$100 000 were established decades ago and may no longer reflect current economic landscapes, healthcare costs and societal values.³ Despite this, these thresholds continue to serve as benchmarks in many studies, including those focused on ophthalmology.⁴ Fixed thresholds can perpetuate a one-size-fits-all approach that may not be applicable and transferrable to various contexts.⁵

Despite the importance of WTP thresholds in guiding healthcare resource allocation, no systematic studies have investigated how these thresholds have evolved over time and influence current decision making. Thus, this study assessed the frequencies of various input parameters used in CEAs in ophthalmology. This study further assessed how WTP thresholds have evolved over time and explored whether current practices align with evolving economic contexts.

Subjects and methods

This study evaluated CEAs assessing diseases of the eye and adnexa from the Tufts Medical Centre CEA Registry, a database of CUA on a wide range of treatments published since 1976. Ethical approval was not required as the study used only published articles.

We systematically extracted and analysed key input parameters from eligible studies, including disease classification, intervention type, WTP thresholds, funding sources, time horizons and discounting rates. The analysis focused on CEAs conducted in the USA, covering publications from 1993 to 2022.

Descriptive statistics were used to summarise the distribution of WTP thresholds, funding sources and intervention types. Trends in WTP thresholds over time were assessed to examine changes in cost-effectiveness benchmarks. Additionally, WTP thresholds were stratified based on funding sources to evaluate potential associations between funding and the selection of WTP values.

Results

Out of 82 CEAs, all study outcomes included QALY, consistent with the classification of Tuft’s Medical Centre CEA Registry as a CEA registry. Among these, 17 studies reported a healthcare perspective, and six studies reported a societal perspective. A summary of the findings is presented in table 1.

Table 1. Characteristics of the 82 cost-effectiveness analyses in the USA.

	Result, n (%)
WTP threshold (US$)
10 000	2 (2.4)
20 000	6 (7.3)
50 000	34 (41.5)
100 000	32 (39.0)
150 000	7 (8.5)
Funding sources
Government	27 (32.9)
Nonprofit	24 (29.3)
Pharmaceutical/medical device industry	17 (20.7)
Healthcare organisation	4 (4.9)
Professional membership organisation	1 (1.2)
University/academic	1 (1.2)
Other	9 (11.0)
None	20 (24.4)
Intervention type(s)
Pharmaceutical	33 (40.2)
Surgical	33 (40.2)
Medical procedure	21 (25.6)
Medical device	10 (12.2)
Screening	9 (10.1)
Diagnostic	3 (3.7)
Health education or behaviour	2 (2.4)
Care delivery	2 (2.4)
Disease classification
Choroid and retina	35 (42.7)
Lens	14 (17.0)
Sclera, cornea, iris and ciliary body	10 (12.2)
Glaucoma	9 (11.0)
Eyelid, lacrimal system and orbit	4 (4.9)
Diabetes mellitus	4 (4.9)
Vitreous body and globe	4 (4.9)
Congenital malformations of the eye, ear, face and neck	3 (3.7)
Visual disturbances and blindness	3 (3.7)
Ocular muscles, binocular movement, accommodation and refraction	2 (2.4)
Genetic carrier and genetic susceptibility to disease	1 (1.2)
Mycoses	1 (1.2)
Time horizon
Lifetime (years)	33 (40.2)
1–10	22 (26.9)
11–20	18 (22.0)
21–30	3 (3.7)
31–40	6 (7.3)
41–50	3 (3.7)

WTP, willingness-to-pay.

Studies often reported WTP thresholds of US$50 000 (41%), US$100 000 (39%), US$150 000 (9%) and US$20 000 (7%). The earliest usage of a US$150 000 WTP threshold was in 2019. All studies used a discount rate of 3.0% for both costs and QALYs. Studies were commonly funded by the government (33%), followed by nonprofit organisations (29%) and pharmaceutical companies (17%). Pharmaceutical-funded studies often used WTP thresholds of US$100 000 (29%), US$150 000 (29%) and US$50 000 (14%). Government-funded studies favoured US$50 000 (44%) and US$100 000 (19%), whereas nonprofit-funded studies commonly reported US$50 000 (38%) and US$100 000 (38%).

The most common intervention types were surgical (40%) and pharmaceutical (40%), followed by medical procedures (26%) and medical devices (12%). The most common disease classifications studied included diseases of the choroid and retina (43%), lens (17%), and sclera, cornea, iris and ciliary body (12%).

Discussion

In this study of 82 CEAs in ophthalmology in the USA, the most frequently used parameters were US$50 000–$100 000 WTP thresholds, lifetime time horizon and 3.0% discount for both costs and QALYs. Studies were often publicly funded or funded by non-profit organisations. The diseases of the choroid and retina was the disease classification most often investigated, and surgical or pharmaceutical options were the intervention types most often analysed.

A higher proportion of studies reported a healthcare perspective compared with those reporting a societal perspective. The inclusion of societal perspectives accounts for a broader range of costs, such as productivity losses and informal care, naturally resulting in higher ICERs and potentially higher WTP thresholds.

Recent studies have begun to use a WTP threshold of US$150 000. This is in line with recent studies demonstrating increased cost-effectiveness with values between US$100 000 and US$150 000.⁶ Although the WTP threshold of US$50 000–US$100 000 is largely used by policymakers and researchers, it was established in 1982 and does not account for changes in the economic landscape and inflation over time.⁷ The increased prevalence of US$150 000 WTP thresholds among pharmaceutical-funded studies raises questions about why different thresholds are selected and whether these decisions are driven by evidence, funding sources or other factors.

WTP thresholds vary worldwide. Values of £20 000–£30 000 and US$50 000 have been applied in the UK and USA, respectively. These thresholds were originally developed for disability-adjusted life years, and due to the lack of specific guidelines for QALYs, researchers have historically adopted similar thresholds for QALYs.⁸ The WHO has recommended thresholds of 1–3 times the gross domestic product per capita.⁹

CEA thresholds in the USA are notably higher than those in the UK, reflecting differences in healthcare funding and decision-making processes among the geographic regions.¹⁰ Increased thresholds may reflect a higher priority in innovation and willingness to invest in healthcare, whereas lower thresholds may emphasise cost containment within the publicly funded National Health Service (NHS) in the UK.¹⁰ Additionally, fixed thresholds often used in the USA may introduce bias in the context of changing economic conditions or advancements in technologies, whereas a context-driven flexible approach to WTP thresholds reflects a dynamic way to assess cost-effectiveness while introducing uncertainty in decision-making.¹⁰ Differing WTP thresholds may also reflect the funding sources of differing healthcare systems. Publicly funded systems have a stronger imperative to allocate resources efficiently, leading to lower thresholds, whereas in the US system, a mix of public and private funding can tolerate higher thresholds owing to a different set of economic pressures and priorities.¹⁰

Evidence has shown increased WTP for a QALY in society compared with the currently used thresholds for economic evaluations.¹¹ Thus, the emergence of new treatments and therapies is a direct result of healthcare allocation legislated by the government.¹¹ WTP thresholds may need to be reassessed periodically to remain relevant, particularly in the climate of fluctuating economic landscapes across different continents.

WTP thresholds have profound implications for policy decision-making, particularly in how healthcare resources are allocated and the extent to which treatments are deemed cost-effective. Fixed WTP thresholds, such as the commonly cited US$50 000 or US$100 000 per QALY in the USA, may no longer accurately reflect current economic conditions or societal values. Despite merit in maintaining fixed thresholds to avoid the risk of unfair or inefficient decisions, flexible thresholds offer evidence-based approaches to address inequities arising from rigid standards. The National Institute for Health and Care Excellence in the UK introduced a ‘severity-based’ approach, allowing for higher thresholds for certain conditions, to better reflect societal preferences and reduce inequities.¹² Variations in WTP thresholds globally underscore the importance of balancing consistency with contextual flexibility. Policymakers operating within publicly funded healthcare systems, like the NHS, prioritise cost containment, often resulting in lower thresholds, whereas mixed public–private systems, such as in the USA, demonstrate higher tolerance for innovation and investment, reflected in higher thresholds. Periodic reassessment of these thresholds, informed by societal WTP and evolving economic landscapes, would ensure that health policies remain equitable and effective in addressing population needs.

In ophthalmology, where interventions range from pharmaceutical treatments to complex surgeries, understanding these trends is essential to ensure CEA findings remain relevant and aligned with current healthcare priorities. These results highlight the need to consider flexible and current input parameters in CEAs to ensure relevance and applicability in today’s economic and healthcare advancements. The persistence of outdated and fixed WTP thresholds could lead to suboptimal decision-making in healthcare policy and resource allocation. Additionally, expanding the scope of funding sources and intervention types in CEAs could provide a more comprehensive understanding of cost-effectiveness in ophthalmology, which would support the development of effective and equitable healthcare strategies.

Data availability statement

No data are available.