Cardiovascular magnetic resonance (CMR) is an accurate, non-invasive diagnostic option for patients with suspected coronary artery disease (CAD). However, there are diagnostic alternatives for patients at low-to-intermediate risk. Several factors influence clinical decision-making, so how can the cost-effectiveness of CMR for the detection of CAD be calculated?
Previous research had made an evaluation of the clinical and cost impacts of CMR for low-to-intermediate risk patients with suspected significant CAD, but the cost-effectiveness of CMR compared to relevant comparators - such as single-photon emission computed tomography (SPECT), coronary computed tomography angiography (CCTA) or invasive coronary angiography (ICA) – had not been analyzed and summarized.
In this study, a team affiliated with institutions in the US, Australia, Canada, Germany, Malaysia, Mexico, South Africa, Switzerland, Taiwan, and the UK, set out to create a cost-effectiveness calculator for CMR which would be usable worldwide.
Diagnostic options and factors in clinical decision making
Alternatives to CMR for the diagnosis of suspected CAD were outlined, including SPECT, CCTA, ICA, and ergometry, as well as conservative management and aggressive management. The researchers also acknowledged the factors that can influence clinical decision-making, such as imaging costs, local availability of imaging modalities and expertise, and prevalence of the underlying disease.
Calculating the cost-effectiveness profile of CMR
It was noted that there was a lack of clarity on the specific cost-effectiveness profile of CMR compared to its relevant comparators, especially considering the continuing evolution of imaging performance. With that in mind, the study set out a two-step approach:
1. To analyze and summarize the comparative cost-effectiveness of CMR imaging for the assessment of stable chest pain syndromes, based on the existing medical literature.
2. To create a unique cost-effectiveness calculator that could be used worldwide to estimate lifetime discounted costs and cost-per-quality-adjusted life-year (QALY) for CMR versus its relevant comparator techniques.
Search strategy and data extraction
A systematic review of existing literature was conducted using the Tufts Cost-Effectiveness Analysis Registry, which contains 8,000 English-language cost-per-QALY studies, and PubMed. The reference lists of every identified CMR cost-per-QALY or relevant review study were searched to identify additional CMR cost-effectiveness studies missed by other methods. Only studies that used CMR as an imaging strategy to assess CAD as the primary clinical condition were included.
Each study was reviewed to extract relevant data, and information such as the setting of the analysis, comparators included, the analytic perspective taken, analytic time horizon taken, main conclusion on the cost-effectiveness of CMR, and key drivers of the results was summarised. Author assessments were used to determine whether CMR represented a cost-effective option or cost-ineffective option for a given paper, in relation to country-specific cost-effectiveness thresholds.
Development of the CMR cost-effectiveness calculator
A CMR Markov (state-transition cohort) model developed for a previous CMR cost-per-QALY study was used to build a user-friendly CMR cost-effectiveness meta-model. The model projects lifetime discounted QALY and cost outputs for five strategies:
1. No Imaging
Patients with normal findings were presumed to be free of obstructive CAD and were managed accordingly. In the No Imaging strategy, patients were initially managed without any investigations. The Markov model had four major health states: no clinical major cardiovascular events (MACE), history of one MACE, history of more than one MACE, and all-cause death.
The meta-model approximates the lifetime discounted QALY and cost results for a given imaging strategy based on user-entered population - and system-level inputs, such as the prevalence of CAD, costs of imaging and procedures, and other model inputs.
CMR was found to be cost-effective in two-thirds of studies
The search of CMR cost-effectiveness studies yielded 39 studies, of which 15 met the inclusion criteria. Reasons for 17 studies being excluded included unoriginal research or a focus on the cost-effectiveness of CMR for heart failure patients (as opposed to CAD).
CMR was found to be cost-effective versus its relevant comparator in ten out of 15 studies. Among these ten studies, the most common comparators to CMR were strategies that used ICA or SPECT. Three studies compared CMR versus strategies that used CCTA, and one directly compared CMR to a No Imaging strategy. Two studies found CCTA to be more cost-effective than CMR, with results generally driven by CCTA’s superior accuracy. Three studies found unclear cost-effectiveness among the imaging strategies analyzed.
Of the 15 studies analyzed, nine found that underlying CAD prevalence was a key driver of cost-effectiveness findings, and four cited changes in imaging prices as a factor.
CMR cost-effectiveness calculator results
This table shows the fitted coefficients for the lifetime discounted QALY and cost results for the No Imaging strategy, and incremental QALY and cost results for the CMR, CCTA, SPECT, and ICA strategies.
The calculator (meta-model) was used to closely replicate the incremental cost-effectiveness results for CCTA compared to a No Imaging strategy and CMR. Whether CMR or CCTA showed superior cost-effectiveness depended on which previous model (Genders et al. or Ge et al.) the inputs for the meta-model were taken from. When the Ge et al. model input values were used, CMR dominated CCTA, and when the meta-model was mainly fed with Genders et al. inputs, CMR dominated CCTA. These findings, and other cost-effectiveness results for selected imaging strategies and scenarios, are displayed in this table.
CMR ‘produces health at reasonable value’
Most (62%) literature reviewed by the study concluded that “CMR-based diagnostic strategies produced health at a reasonable value compared to setting-specific cost-effectiveness thresholds” and that “when CMR is not available, CCTA represents a cost-effective alternative”.
CMR cost-effectiveness calculator usable in clinical settings
While acknowledging an overrepresentation of settings in the US, Germany, and the UK in the published literature reviewed, the researchers are satisfied that they have “developed a CMR cost-effectiveness calculator that end-users” including physicians and hospital decision-makers “can use to approximate setting-specific cost-effectiveness results”.
The study highlights that “such tools can assist in obtaining the most realistic estimates of overall value from options available to diagnose and treat significant CAD”.