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Cost effectiveness of coronary angiography and calcium scoring using CT and stress MRI for diagnosis of coronary artery disease |
Dewey M, Hamm B |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology The study examined six strategies for the diagnosis of coronary artery disease (CAD). In particular, three new strategies were compared with three conventional approaches. The new options were coronary angiography using multislice computed tomography (MSCT), calcium scoring using electron-beam computed tomography (EBT), and dobutamine stress magnetic resonance imaging (MRI). The three conventional modalities were conventional coronary angiography (CATH), exercise ECG (Ex-RCG), and dobutamine stress echocardiography (ECHO). CATH was used as the gold standard, to confirm the accuracy of the other strategies.
Economic study type Cost-effectiveness analysis.
Study population The study population comprised a hypothetical cohort of patients with suspected CAD. Individuals aged between 30 and 69 years appear to have been considered.
Setting The setting was secondary care and a hospital. The economic study was carried out in Germany.
Dates to which data relate The effectiveness data were derived from studies published between 1979 and 2006. No dates for resource use were reported. The price year was not explicitly stated.
Source of effectiveness data The clinical and epidemiological inputs of the model were:
cardiovascular risk factors (age and gender) and anginal symptoms, which were used to calculate the different pre-test likelihood of disease;
the sensitivity and specificity of the diagnostic modalities;
the rate of non-diagnostic examinations; and
the rate of complications with each strategy.
Modelling To determine the costs and benefits of the different diagnostic approaches, a decision tree reflecting the German situation was constructed on the basis of a previous model. The structure of the decision model was depicted graphically for all strategies. The time horizon of the analysis appears to have been 10 years, although all tests were conducted in the short term.
Sources searched to identify primary studies With the exception of the accuracy of CATH, which was set at 100% (both sensitivity and specificity) by definition, the clinical data were derived from published studies. The sensitivity, specificity and rates of non-diagnostic examinations with MSCT were obtained from a meta-analysis of 12 prospective studies. Other data were derived from meta-analyses, reviews and original studies. However, details of the primary sources were not given.
Methods used to judge relevance and validity, and for extracting data The authors stated that a review of the literature was undertaken to identify the primary studies. However, no information on the approaches used to identify, select and combine the primary studies was provided.
Measure of benefits used in the economic analysis The summary benefit measure used was the number of correctly diagnosed patients. This was derived using a modelling approach.
Direct costs The viewpoint of the German reimbursement system was considered in the analysis of the direct costs. The cost categories included were diagnostic tests under examination, subsequent tests, treatment of complications (myocardial infarction) and the diagnosis of a patient as false negative. The cost of myocardial infarction comprised hospitalisation and rehabilitation. The unit costs were presented separately from the resource quantities for several items. Resource use was based on authors' assumptions. The costs were derived using reimbursement rates from German sources such as the German outpatient reimbursement system and the German Diagnosis Related Groups. The drug costs were obtained from industry prices for outpatient physicians. The costs of complications were discounted at an annual rate of 5%. The price year was not explicitly stated.
Statistical analysis of costs Statistical analyses of the costs were not performed.
Indirect Costs Productivity costs associated with the absence of a patient from work due to myocardial infarction were included in the analysis on the basis of the gross domestic product. The authors defined the length of work absence.
Sensitivity analysis A deterministic sensitivity analysis was carried out to test the robustness of the cost-effectiveness results to variations in the accuracy of noninvasive tests, the complication rate of CATH, complication-related costs and the cost of CATH. Accuracy was varied using published confidence intervals, while other alternative values appear to have been set by the authors. A break-even analysis was also performed for MSCT coronary angiography, from the perspective of the health care providers. This considered the costs of several items such as purchase of the scanner, construction and installation, electricity requirements and maintenance.
Estimated benefits used in the economic analysis The estimated benefits were only presented graphically. The highest accuracy was associated with CATH (gold standard), followed by MSCT, EBT, MRI and ECHO.
Cost results The total costs were not reported.
Synthesis of costs and benefits An average cost-effectiveness ratio (ACER; i.e. the cost per correctly identified patient) was calculated in order to combine the costs and benefits of the alternative strategies.
In general, the cost per correctly identified patient decreased dramatically with increasing pre-test likelihood for all strategies.
For patients with a pre-test likelihood of CAD in the range of 10 to 50%, MSCT was the most cost-effective option with an ACER of EUR 4,435 (10% likelihood) to EUR 1,469 (50% likelihood).
Ex-ECG was more cost-effective than ECHO at a likelihood of 10% (ACER of EUR 5,313 versus EUR 5,583), while ECHO was the most cost-effective traditional approach for patients with a likelihood of 20% (EUR 3,207) to 30% (EUR 2,416).
At a pre-test likelihood of 60%, MSCT and CATH were equally effective, with an ACER of EUR 1,345, while CATH was the most cost-effective for a pre-test likelihood of at least 70% with ACERs ranging from EUR 1,153 (70%) to EUR 807 (100%).
For a likelihood of 30 to 40%, EBT was more cost-effective than the other traditional modalities, but not MSCT, with ACERs ranging from EUR 2,345 (30% likelihood) to EUR 1,897 (40% likelihood). However, for a likelihood of 50% or greater, CATH was more cost-effective than EBT.
MRI was not cost-effective for any pre-test likelihood.
The sensitivity analysis showed that when the accuracy was varied across the published confidence interval, MSCT was the most cost-effective strategy up to a pre-test likelihood of 60% (highest accuracy) and 50% (lowest accuracy). In general, MSCT remained the most economically attractive option unless unfavourable scenarios were considered. The break-even analysis from the perspective of the health care system showed that MSCT would become a profitable diagnostic modality only after a period of 64 months (23 months in a high-referral centre), or if reimbursement were three times higher than with the present outpatient reimbursement system in Germany.
Authors' conclusions Coronary angiography using multislice computed tomography (CT) was the most cost-effective procedure for a pre-test likelihood of disease up to 50%. When the pre-test probability of coronary artery disease (CAD) was very high (above 60%), CATH was the preferred diagnostic option.
CRD COMMENTARY - Selection of comparators The choice of the comparators was appropriate as several new and traditional diagnostic strategies were considered. The authors stated that myocardial stress scintigraphy was not considered as a relevant comparator because it had already been shown not to be cost-effective in Germany. You should decide whether they are valid comparators in your own setting.
Validity of estimate of measure of effectiveness The clinical inputs of the model were derived from the literature. However, no systematic search of data was reported and little information on the design and other characteristics of the primary studies was given. This limits the possibility of assessing the validity of the clinical estimates. The methods used to combine primary estimates from amongst those available in the literature were not described. However, some estimates of test accuracy were taken from published meta-analyses. Some key model inputs were investigated in the sensitivity analysis on the basis of ranges found in published studies. Validity of estimate of measure of benefit The summary benefit measure was specific to the disease considered in the study and will not be easy to compare with the benefits of other health care interventions. However, it represents the natural end point of screening programmes. An evaluation of the impact of the screening strategies on both survival and quality of life would have been interesting.
Validity of estimate of costs The cost analysis was carried out from a modified societal perspective in which costs relevant to the reimbursement authorities, as well as some productivity losses, were included. The unit costs were presented for most items, especially the diagnostic tests. Resource use was based on authors' opinions about the number of tests performed. Conventional sources of data were used for both the direct and indirect costs. Statistical analyses of the costs were not performed and only a few costs were varied in the sensitivity analysis. The price year was not explicitly reported, which may have important implications for the generalisability of the analysis.
Other issues The authors stated that the current findings updated the results from a previous study they had undertaken using a published model; some differences with the prior analyses were pointed out. The issue of the generalisability of the study results to other settings was not explicitly addressed, although sensitivity analyses performed on key model inputs help to enhance the external validity of the analysis. The authors noted some limitations of their study. First, given to the use of modelling, the relevance of the analysis for clinical practice might be reduced in comparisons with studies based on clinical trials. Second, the use of quality-adjusted life-years would have been more interesting, but they are not the best benefit measure for the evaluation of imaging studies. Third, the published data on accuracy provided very wide estimates, which had a strong impact on the results of the analysis. Finally, the costs of treating CAD were not modelled, although they are likely to represent a relevant item. The results of the analysis were presented selectively.
Implications of the study The study results support the use of MSCT for the diagnosis of CAD in patients with a pre-test probability of disease below 50% and the use of CATH for those with a pre-test likelihood above 60%. The study results highlighted the importance of the estimation of pre-test likelihood of disease as a key criterion in selecting the most appropriate diagnostic strategy.
Bibliographic details Dewey M, Hamm B. Cost effectiveness of coronary angiography and calcium scoring using CT and stress MRI for diagnosis of coronary artery disease. European Radiology 2007; 17(5): 1301-1309 Other publications of related interest Because readers are likely to encounter and assess individual publications, NHS EED abstracts reflect the original publication as it is written, as a stand-alone paper. Where NHS EED abstractors are able to identify positively that a publication is significantly linked to or informed by other publications, these will be referenced in the text of the abstract and their bibliographic details recorded here for information.
Dewey M, Hamm B. Comparison of the cost effectiveness of the most common diagnostic methods for coronary artery disease. Dtsch Med Wochenschr 2004;129:1415-9.
Garber AM, Solomon NA. Cost-effectiveness of alternative test strategies for the diagnosis of coronary artery disease. Ann Intern Med 1999;130:719-28.
Patterson RE, Eisner RL, Horowitz SF. Comparison of cost-effectiveness and utility exercises ECG, single photon emission computed tomography, positron emission tomography, and coronary angiography for diagnosis of coronary artery disease. Circulation 1995;91:54-65.
Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Calcinosis /diagnosis /economics /radiography; Coronary Angiography /economics; Coronary Disease /diagnosis /economics; Cost-Benefit Analysis; Decision Trees; Echocardiography, Stress /economics; Electrocardiography /economics; Female; Humans; Magnetic Resonance Imaging /economics; Male; Middle Aged; Sensitivity and Specificity; Tomography, X-Ray Computed /economics AccessionNumber 22007001029 Date bibliographic record published 30/11/2007 Date abstract record published 30/11/2007 |
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