Disclaimer: The Medical Advisory Secretariat uses a standardized costing method for its economic analyses of interventions. The main cost categories and the associated methods from the province’s perspective are as follows:
Hospital: Ontario Case Costing Initiative cost data are used for in-hospital stay, emergency visit and day procedure costs for the designated International Classification of Diseases (ICD) diagnosis codes and Canadian Classification of Health Interventions procedure codes. Adjustments may be required to reflect accuracy in estimated costs of the diagnoses and procedures under consideration. Due to the difficulties of estimating indirect costs in hospitals associated with a particular diagnosis or procedure, the secretariat normally defaults to considering direct treatment costs only.
Nonhospital: These include physician services costs obtained from the Ontario Schedule of Benefits, laboratory fees from the Ontario Schedule of Laboratory Fees, drug costs from the Ontario Drug Benefit Formulary, and device costs from the perspective of local health care institutions whenever possible or its manufacturer.
Discounting: For cost-effectiveness analyses, a discount rate of 5% is applied as recommended by economic guidelines.
Downstream costs: All numbers reported are based on assumptions on population trends (i.e. incidence, prevalence and mortality rates), time horizon, resource utilization, patient compliance, healthcare patterns, market trends (i.e. rates of intervention uptake or trends in current programs in place in the Province), and estimates on funding and prices. These may or may not be realized by the system or individual institutions and are often based on evidence from the medical literature, standard listing references and educated hypotheses from expert panels. In cases where a deviation from this standard is used, an explanation is offered as to the reasons, the assumptions, and the revised approach. The economic analysis represents an estimate only, based on the assumptions and costing methods that have been explicitly stated above. These estimates will change if different assumptions and costing methods are applied to the analysis.
The objective of this economic analysis is to determine the cost effectiveness of stress contrast ECHO for the diagnosis of patients with suspected CAD, when compared to the following cardiac imaging modalities: stress ECHO (without contrast), SPECT, cardiac MRI, and CT angiography. The relative cost-effectiveness of these five non-invasive cardiac imaging technologies was assessed in two patient populations: a) out-patients presenting with stable chest pain; and b) in-patients presenting with acute, unstable chest pain. Note that the term “contrast ECHO” used in the following sections refers to stress ECHO performed with the availability of contrast medium if needed, due to poor image quality.
Economic Analysis Overview
For the two patient populations, decision-analytic cost-effectiveness analyses were conducted to evaluate the relative cost-effectiveness of the five imaging technologies. Two decision analytic models were developed for these patient populations with two reported outcomes: the cost per accurate diagnosis of CAD and the cost per true positive diagnosis of CAD. The physician and hospital costs for the were taken from 2009 Ontario Health Insurance Plan (OHIP) and the Ontario Case Costing Initiative (OCCI) administrative databases.(49
) A budget impact analysis (BIA) was them performed to assess the effect of replacing a certain proportion of stress contrast ECHO tests with other cost-effective, non-invasive modalities. The costs presented in this BIA were estimated from Ontario data sources from 2009; the volumes of tests performed were estimated from data from fiscal years 2002 to 2008.
Economic Literature Review
The purpose of the systematic review of economic literature was to identify, retrieve, and summarize studies evaluating the cost-effectiveness of selected cardiac imaging tests for the diagnosis of CAD. Medline and the National Health Service Economic Evaluation Database (NHSEED) were searched from their inception up to October 2009. Included studies were those full economic evaluations describing both costs and consequences of a) CT angiography, b) Cardiac MRI, c) SPECT, d) stress ECHO, and e) stress contrast ECHO in CAD diagnosis. Article selection was performed by independent pairs of researchers. Target data for extraction included: study first author and year of publication, imaging tests compared, type of economic analysis, reported costs and outcomes, incremental cost-effectiveness ratio (ICER), currency, and patient characteristics (i.e. known or suspected CAD and risk of CAD). The primary outcome of interest was the ICER of each imaging test in relation to another test of interest.
Literature Search Results
A total of 883 non-duplicate citations were found from the two electronic databases after applying the literature search strategy. Based on the content of their abstracts, 147 full-text articles were retrieved for further assessment of their inclusion/exclusion. Of these, 122 were rejected, leaving 25 articles for inclusion. Following the data extraction process, 13 studies were excluded (16
), with 12 studies being ultimately selected for analysis. (62
Characteristics of Included Studies
From the 12 studies included, eight studies assessed the cost-effectiveness of two of the selected imaging tests (65
), three evaluated three concomitant technologies (62
), and one study evaluated five technologies.(63
Five studies were cost-effectiveness analyses, where the most common outcome was cost per correct/successful CAD diagnosis.(62
) The other seven studies were cost-utility analyses using cost per quality adjusted life years (QALYs) as their primary outcome.(64
) The time-horizon used across the included studies ranged from 30 days to lifetime, with five studies having 25 years or more of follow-up.(64
) The remaining studies used 18 months (71
), 3 months (73
), and 30 days of analytical time horizon.(67
) Four studies did not report the time-horizon used in their analysis.(62
All included studies evaluated at least one form of ECHO against one of the other remaining selected imaging tests.(62
) The cost-effectiveness of SPECT was studied in nine studies.(62
), three studies assessed CT angiography in comparison to stress ECHO or MRI (63
), while cardiac MRI was compared to each of the three other selected imaging tests in two studies.(63
) No full economic analysis between CT angiography and SPECT was found in the published literature.
Cost-effectiveness results for strategies involving stress contrast ECHO were not found in the systematic literature review performed in this report. Comparative cost-effectiveness was rather evaluated for stress ECHO alone without contrast agents. As a consequence, no further results are presented here for contrast ECHO technology.
Conclusion of systematic review
Overall, CT angiography was found to be cost-effective or cost-saving in all four of the comparisons for that technology; stress ECHO was found cost-effective in eight of the 13 comparisons in which it was evaluated; and SPECT was found cost-effective in three of the nine comparisons. Cardiac MRI was not found to be cost-effective or cost-saving in any of the four comparisons found.
According to the published economic data, CT angiography is often found to be cost-effective when compared to other technologies. SPECT and stress ECHO were also found to be cost-effective in several of the comparative studies examined, while cardiac MRI was not cost-effective in any study. Limitations to these conclusions apply, such as the analyses found in the literature evaluated other forms of the selected cardiac imaging tests which might change the proposed relative cost-effectiveness.
Decision analytic Cost Effectiveness Analysis
This study was designed as a cost effectiveness analysis, with primary results reported as incremental cost per true positive diagnosis, or incremental cost per accurate diagnosis.
Target Population and Perspective
Two populations were defined for evaluating the cost-effectiveness of an accurate diagnosis (i.e. true positive and true negative diagnoses) of CAD: a) out-patients presenting with stable chest pain; and b) in-patients presenting with acute, unstable chest pain. The first population was defined as persons presenting with stable chest pain, with an intermediate risk of CAD following physical examination and a graded exercise test, as defined by the American College of Cardiology / American Heart Association 2002 Guideline Update for the Management of Patients with Chronic Stable Angina.(75
) The second population was defined as persons presenting to emergency for acute, unstable chest pain, and who are admitted to hospital, as defined by the American College of Cardiology / American Heart Association 2007 Guidelines for the Management of Patients with Unstable Angina/Non-ST-Elevation Myocardial Infarction.(76
The analytic perspective was that of the Ontario Ministry of Health and Long-Term Care (MOHLTC).
Comparators and Parameter Estimates
The imaging technologies that were compared in the current cost-effectiveness analysis included: CT angiography, stress ECHO (with and without contrast mediums, cardiac perfusion stress MRI, and attenuation-corrected SPECT. Test characteristic estimates (i.e., specificity, sensitivity, accuracy) for each cardiac imaging technology were obtained from the systematic review and meta-analysis conducted by MAS and the MOHLTC. shows a list of the parameters with corresponding 95% confidence intervals used for both the outpatient and inpatient decision-analytic cost-effectiveness models.
Summary parameter estimates for contrast ECHO tests
The average wait-time for each cardiac imaging test was measured as the additional days needed to wait for a non-invasive test compared to the average wait time for a typical graded exercise stress test (GXT). The proportion of tests deemed uninterpretable by expert opinion is shown with a corresponding range of high and low values. The probability of receiving pharmacological stress versus exercise stress is not listed, but reported here for completeness: approximate values of 30% for the stable, outpatient population and 80% for the unstable, inpatient population.
Time Horizon & Discounting
The time horizon for both decision-analytic models (i.e. for outpatient and inpatient populations) was the time required to determine an accurate, or true positive diagnosis of CAD. As a result, the actual time taken to determine the CAD status of patients may differ across non-invasive test strategies.
Model Structure and Outcomes
provides a simplified illustration of the decision-analytic model structure used for the outpatient and inpatient populations. The following two simplifying assumptions were made for the models:
Decision analytic model used to evaluate the cost-effectiveness of cardiac imaging technologies for the diagnosis of CAD
- When results of the first cardiac imaging test are un-interpretable, a patient will undergo a second cardiac test, This will be one of the four remaining tests that were not used as the first test.
- Should a second test be required, the type of stress (pharmacological or exercise) that a patient receives will be the same type of stress as used in the first test.
The short-term outcome presented in this report focuses on an accurate diagnosis of CAD (i.e. true positive and true negative test results). A second outcome of true positive diagnosis was examined for the two models, with results reported in The Relative Cost-effectiveness of Five Non-invasive Cardiac Imaging Technologies for Diagnosing Coronary Artery Disease in Ontario. (74
Various sensitivity analyses were conducted for the outpatient and inpatient populations. First, the prevalence of CAD was varied from 5% to 95% in 5% increments, while all other model estimates were held constant. Willingness-to-pay (WTP) was also varied and a range of results were presented. Second, one-way sensitivity analyses were conducted in which selected estimates were varied over plausible ranges. The varied parameters included sensitivity and specificity estimates, wait times for imaging tests performed in hospital, as well as the costs of CT angiography, ECHO tests, and cardiac MRI. A third series of sensitivity analyses was conducted that specifically addressed the possibility of unavailable imaging technologies.
Resource Use and Costs
Resource use and costs were derived from Ontario data sources: the OHIP and OCCI administrative databases.(49
) The cost of conducting each cardiac test was calculated as the sum of the test’s respective professional fees and technical fees, as described in the Ontario Schedule of Benefits and listed in .
List of cardiac imaging tests and associated OHIP 2009 costs
Note that for ECHO tests with available contrast agent, the cost for the contrast medium was added whenever the contrast was used in the event of uninterpretable ECHO test result. The cost of this contrast medium was estimated as $170 per vial (single use) through consultation with industry experts. Only this cost was added to the base test cost of contrast ECHO. In general, where an imaging test result was uninterpretable, an additional cost of follow-up with the patient (physician fee) was incurred, as well as the cost for conducting another cardiac imaging test. For out-patients presenting with stable chest pain, a consultation professional fee of $30.60 (OHIP code A608 for “partial assessment”) was used after an uninterpretable test result (one time cost).
In the case of patients presenting with acute, unstable chest pain, costs for inpatient hospitalization were also included in the model. The total cost of hospitalization was calculated based on the average wait time for each cardiac imaging test and a cost per diem for each day spent in hospital. An additional consultation fee was also used only for the inpatient population: $29.20 (OHIP code C602 for “subsequent visit- first five weeks”) was used for each inpatient day spent in hospital.
The WTP must be determined by the MOHLTC. As such, all reasonable WTP values presented in the Results and Discussion section are interpreted at two WTP ‘anchors’ representing the estimated cost of the most expensive non-invasive test considered in our model (cardiac MRI perfusion, $804) and the estimated cost of a coronary angiography ($1,433). These anchors are only intended to guide discussion.
Note that the following points might be useful in determining the WTP:
- An “accurate diagnosis” of CAD can be obtained through a coronary angiography for $1,433. It would thus be reasonable to expect the WTP for an accurate diagnosis through a non-invasive test to resemble this amount; however, an accurate diagnosis does not include the value or benefit of providing additional diagnostic or prognostic information from either non-invasive imaging or coronary angiography
- The MOHLTC is currently willing to pay up to $804 for a non-invasive test with less-than-perfect diagnostic accuracy. Its willingness to pay for an accurate diagnosis from such a test thus appears to be greater than $804.
- While coronary angiography is invasive, the other tests are non-invasive and would presumably be of greater value (i.e., incur a higher premium). These tests do, however, impose risks not applicable to coronary angiography, such as increased radiation exposure and adverse reaction to contrast agents
- These tests are not perfectly accurate. An accurate diagnosis from such a test may be valued less than one from a coronary angiography
Results and Discussion
As shown in and , stress contrast ECHO was the least costly strategy in both stable outpatients and acute inpatients. In stable outpatients, however, CT angiography showed greater effectiveness and appeared to dominate all strategies, other than contrast ECHO. Whether contrast ECHO or CT angiography is cost-effective for such patients thus depends on the willingness-to-pay (WTP) for an accurate diagnosis of CAD, which we have considered at two anchors: $804 and $1,433 per accurate diagnosis. Since CT angiography has an ICER of $1,527 per accurate diagnosis compared to contrast ECHO, contrast ECHO appears to be more cost-effective than CT angiography at either anchor. In acute inpatients, CT angiography did not appear cost-effective in the base case analysis due to its assumed longer hospital wait time. As such, contrast ECHO appeared clearly cost-effective at both anchors.
Cost-effectiveness analysis base case results for stable outpatients
Cost-effectiveness analysis base case results for acute inpatients
The analysis of the prevalence of CAD revealed that, in stable outpatients, contrast ECHO was more cost-effective at lower prevalence rates of CAD. At the two WTP anchors of $804 and $1433 per accurate diagnosis, contrast ECHO was considered cost-effective in the stable outpatient population when the prevalence of CAD was less than 70% or 50% respectively, with CT angiography appearing cost-effective otherwise. In acute inpatients, contrast ECHO appeared cost-effective at both WTP anchors at any prevalence of CAD. When the hospital wait times were assumed to be normalized across all tests, contrast ECHO still appeared cost-effective, with the sole exception that CT angiography appeared cost-effective only at the higher WTP anchor and when the prevalence of CAD was greater than 80%.
Contrast ECHO was found to be generally cost-effective in both stable outpatients and acute inpatients. In the stable outpatient population, contrast ECHO was more cost-effective at lower prevalence rates of CAD, while in the acute inpatient population stress ECHO appeared to be the most cost-effective strategy at any prevalence of CAD.
Budget Impact Analysis
The budget impact analysis (BIA) was performed taking the perspective of the MOHLTC and includes both physician and hospital (clinic) costs of non-invasive cardiac imaging tests. Volumes of cardiac tests in Ontario were taken from administrative databases (OHIP, DAD, NACRS) for fiscal years 2004 to 2008. (74
) The following technologies were considered in the current BIA for the diagnosis of CAD: ECHO (including both stress and stress with contrast agent available), nuclear cardiac imaging (including MPI and SPECT tests), cardiac MRI, and CT angiography.
In the current BIA, the effect of moving a certain proportion of the volume of specific tests to another, substitute technology was assessed for various scenarios. These scenarios are presented irrespective of whether a technology was found to be cost-effective and are reported as general reference tables. To summarize briefly, stress contrast ECHO tests are the second least expensive of the compared cardiac imaging modalities; stress ECHO without contrast is the least expensive. When the volume of contrast stress ECHO tests is shifted to other technologies, all scenarios result in higher projected costs, except for standard stress ECHO tests without contrast agent available. If 25% of the contrast stress ECHO tests is moved to other imaging technologies, ensuing projected costs would be higher (excluding standard stress ECHO): from a small cost difference of about $14.6K per year for CT angiography testing to a large difference of $95.3K for cardiac MRI testing. The largest possible cost difference corresponds to replacing 50% of contrast stress ECHO tests with cardiac MRI imaging ($190.7K per year); the smallest cost difference occurs for replacing 5% of contrast stress ECHO tests with CT angiography ($2.9K per year), excluding standard stress ECHO.