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Comparison of the cost-effectiveness of stress myocardial SPECT and stress echocardiography in suspected coronary artery disease considering the prognostic value of false-negative results |
Lee D S, Jang M J, Cheon G J, Chung J K, Lee M C |
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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 Three different strategies for the diagnosis of coronary artery disease (CAD) were examined.
If a patient was found to have positive results by myocardial single-photon emission computed tomography (SPECT), coronary angiography (CAG) was performed. CAG was not performed if the myocardial SPECT results were negative.
If a patient was found to have positive results by exercise stress echocardiography (Echo), CAG was performed. CAG was not performed if the exercise Echo results were negative.
If a patient was found to have positive results by dobutamine stress Echo, CAG was performed. CAG was not performed if the dobutamine Echo results were negative.
Study population The study population comprised patients with suspected or proven CAD.
Setting The setting was secondary care. The economic study was carried out in South Korea.
Dates to which data relate The effectiveness data were derived from studies dating from 1978 to 2000. The dates to which the prices related were not stated.
Source of effectiveness data The evidence for the final outcomes was derived from a review of the literature.
Modelling A Markov model was used to model the outcomes for undiagnosed and untreated patients, and how the prognosis would change in the correctly diagnosed group by medical treatment, percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG).
Outcomes assessed in the review The outcomes assessed in the review were:
the complication rate of myocardial SPECT and exercise or dobutamine Echo, and the mortality rate;
the complication rate of CAG and the mortality rate;
the annual complication rate without treatment in the general population and the mortality rate;
the annual complication rate in patients with a negative result by stress myocardial SPECT and the mortality rate;
the annual complication rate in patients with a negative result by exercise or dobutamine Echo and the mortality rate;
the sensitivity and specificity of stress myocardial SPECT;
the sensitivity and specificity of exercise or dobutamine Echo;
the non diagnostic rate of dipyridamole/adenosine stress myocardial SPECT, exercise and dobutamine Echo;
the proportion of patients correctly diagnosed who received medical treatment, PTCA or CABG;
the living-to-dying patient ratio in those treated medically and in those undergoing PTCA and CABG;
survival in the medically treated, PTCA and CABG groups;
the quality of life of living patients in the medically treated, PTCA and CABG groups;
the quality of life during the living years of dying patients in the medically treated, PTCA and CABG groups.
The cases of undiagnosed and untreated patients were assumed to follow the natural course of CAD according to their patient group designations (i.e. patients who would have been treated medically, by PTCA, or by CABG). The outcomes assessed for these patients were:
the living-to-dying ratio in the group who would be medically treated, who would receive PTCA, and who would receive CABG;
survival in the medically treated, CABG and PTCA groups;
the quality of life during the living years of living patients in the medically treated, PTCA, and CABG groups; and
the quality of life during the living years of dying patients in the medically treated, PTCA and CABG groups.
Study designs and other criteria for inclusion in the review Sources searched to identify primary studies Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included Approximately 24 primary studies were included in the analysis.
Methods of combining primary studies Investigation of differences between primary studies Results of the review The complication rate of myocardial SPECT and exercise or dobutamine Echo was 0.0005 (0.05%) and the mortality rate was 0.00005 (0.005%).
The complication rate of CAG was 0.02 (2%) and the mortality rate was 0.0015 (0.15%).
The annual complication rate without treatment in the general population was 0.025 (2.5% per year) and the mortality rate was 0.02 (2.0% per year).
The annual complication rate in patients with a negative result by stress myocardial SPECT was 0.005 (0.5% per year) and the mortality rate was 0.005 (0.5% per year).
The annual complication rate in patients with a negative result by exercise or dobutamine Echo was 0.02 (2% per year) and the mortality rate was 0.02 (2% per year).
The sensitivity of stress myocardial SPECT was 85% and the specificity was 87%.
The sensitivity of exercise or dobutamine Echo was 85% and the specificity was 87%.
The non diagnostic rate was 0 for dipyridamole/adenosine stress myocardial SPECT, 18% for exercise Echo and 9% for dobutamine Echo.
Fifty per cent of the patients correctly diagnosed received medical treatment, 35% received PTCA and 15% received CABG.
The living-to-dying patient ratio was 0.6:0.4 in those treated medically, 0.75:0.25 in those undergoing PTCA and 0.8:0.2 in those undergoing CABG.
Survival was 6 years in the medically treated group, 5 years in the PTCA group and 4 years in the CABG group.
The quality of life during the living years of living patients was 0.8 in the medically treated group, 0.9 in the PTCA group and 0.9 for in the CABG group.
The quality of life during the living years of dying patients was 0.5 in the medically treated group, 0.6 in the PTCA group and 0.5 in the CABG group.
The cases of undiagnosed and untreated patients were assumed to follow the natural course of CAD according to their patient group designations (i.e. patients who would have been treated medically, by PTCA, or by CABG). The outcomes of these patients were as follows.
The living-to-dying ratio was 0.55:0.45 in the group who would be medically treated, 0.5:0.5 in the group who would receive PTCA, and 0.33:0.67 in the group who would receive CABG.
Survival in the medically treated, CABG and PTCA groups, when not treated, was 5 (medically treated), 4 (CABG) and 3 (PTCA) years, respectively.
The quality of life during the living years of living patients was 0.75 in the medically treated group, 0.7 in the PTCA group and 0.6 in the CABG group.
The quality of life during the living years of dying patients was 0.45 in the medically treated group, 0.5 in the PTCA group and 0.5 in the CABG group.
Measure of benefits used in the economic analysis The health benefits used in the economic analysis were the quality-adjusted life-years (QALYs). Utility estimates were derived from Patterson et al. (see Other Publications of Related Interest). In this report, the quality of life associated with each alternative treatment was determined by experts' opinion. A time trade-off model was constructed using these weighting factors of quality of life. A discount rate of 5% was used.
Direct costs It would appear that the direct costs of the third-party payer were included in the analysis. The total cost for each strategy was calculated by summing the direct test costs (test fee) and the indirect test costs. The costs included were for CAG for false-positive results, CAG-related complications, and treatment for complications and death. The costs of the tests and treating complications were obtained from Korean medical insurance data. Discounting was unnecessary, as the costs were incurred during a short time, and was not performed.
The authors provided equations to calculate the total costs for each diagnostic strategy, but did not report the results of these calculations.
Statistical analysis of costs The unit costs were treated as point estimates (i.e. the data were deterministic).
Indirect Costs No indirect costs were included in the analysis.
Currency US dollars ($). No currency conversions were reported.
Sensitivity analysis Sensitivity analyses were performed, both in a general and a specific fashion. In the general sensitivity analysis, the fee for myocardial SPECT and dobutamine Echo was changed to two thirds or 1.5 that of the original fee. For fixed accuracy of myocardial SPECT, the accuracy of Echo was lowered, and vice versa. Finally, the incremental health benefits were cut in half.
The specific sensitivity analysis was carried out in two ways. First, the prognosis of negative or false-negative results by stress Echo was assumed to be better than the initial assumption. The annual cardiac hard event rate of exercise and dobutamine Echo was set at 1% for myocardial infarction and 1% for death. Second, the non diagnostic rate of dobutamine Echo was altered to 19%. In addition, the non diagnostic rate of myocardial SPECT was altered to 9%.
Estimated benefits used in the economic analysis When a discount rate of 5% was applied to the QALY of the time trade-off model of 10 years, the calculated QALY per 10 years was 5.56 years if the patients were correctly diagnosed and treated and 3.83 years if the patients were not diagnosed and thus not treated. In this case the incremental QALYs were 1.73 years.
Cost results The authors did not report the results of their cost calculations. Hence, it was not possible to state the total costs for each diagnostic strategy investigated. The costs of doing nothing (i.e. no diagnostic strategy) were set to zero.
Synthesis of costs and benefits The costs and benefits were combined by calculating an incremental cost-utility ratio (ICUR; additional cost required per QALY). According to the pretest likelihood of CAD, the ICUR was much higher (about 3 to 4 times) for patients with a pretest likelihood of 0.1 than in those patients with a pretest likelihood of 0.6 to 0.9.
When the pretest likelihood was 0.3 or greater, the ICUR of stress myocardial SPECT was lowest, at around $1,400/QALY. When the pretest likelihood was less than 0.3, the ICUR of dobutamine Echo was lowest. For patients with all likelihoods, the ICUR of exercise Echo was the highest.
When the annual complication rates of negative exercise and negative dobutamine Echo results were both assumed to be 0.01 (1%) and both mortality rates 1%, the ICUR of dobutamine Echo was lowest in patients of all pretest likelihoods.
When the non diagnostic rate of dobutamine Echo was 18%, the ICUR of SPECT was lowest in those patients of all pretest likelihoods.
When the non diagnostic rate of SPECT was 9%, the ICUR of dobutamine Echo became lowest when the pretest likelihood was 0.5 or lower.
When the ICURs of these three strategies were compared with that of direct CAG, direct CAG was more cost-effective than SPECT followed by CAG or by dobutamine Echo followed by CAG in those patients with a pretest likelihood of 0.7 or greater.
When the incremental health benefits were cut in half, the ICURs increased but the most cost-effective strategy was SPECT.
When the fee for myocardial SPECT was lowered to two thirds, or the fee for dobutamine Echo was increased to 1.5, the myocardial SPECT strategy was the most cost-effective.
When the fee for SPECT was increased or the fee for echocardiography was reduced, dobutamine Echo became the most cost-effective strategy in those patients with a low pretest likelihood (<0.5).
When the specificity or sensitivity of SPECT was lower (0.7), SPECT was no longer the most cost-effective strategy.
Authors' conclusions In view of the low event rate of false-negative results, the more expensive myocardial single-photon emission computed tomography (SPECT) strategy was more cost-effective than the cheaper stress echocardiography (Echo) strategies.
CRD COMMENTARY - Selection of comparators Although no explicit justification was given for using the do nothing strategy as the comparator, it would appear that this comparator was used to measure the actual value of the intervention. The three interventions under investigation were all competing alternatives in the authors' setting. You should decide if these are widely used health technologies in your own setting.
Validity of estimate of measure of effectiveness The authors did not state that a systematic review of the literature was undertaken to identify all relevant research and minimise any potential problems such as publication bias. The methods and conduct of the review were not reported and it was unclear how the authors combined the results from the primary studies. Hence, there is the possibility that the authors used the data from the available studies selectively. It was also unclear whether some of the results were actually derived from the literature or were based on the authors' assumptions. However, uncertainty in the data was appropriately explored in the sensitivity analyses.
Validity of estimate of measure of benefit The measure of health benefit was obtained through modelling parameters and was discounted by 5% per annum. The methods of derivation remained unclear and it is not certain that they are valid for the patient domain studied.
Validity of estimate of costs The authors did not state the perspective adopted in the economic analysis, but it would appear to have been that of the third-party payer. All the categories of cost relevant to this perspective seem to have been included in the analysis. In addition, for each category of cost, all the relevant costs seem to have been included. The unit costs were obtained from published sources. Uncertainty in this data was appropriately explored in the sensitivity analyses. The authors provided formulae to calculate the total costs for each diagnostic strategy, but did not report the results of these cost calculations. They also did not specify the dates to which the prices related or the exchange rate used to convert their cost results into US$. These two limitations will hamper any possible reflation exercises. Discounting was, appropriately, not performed since the costs were incurred in a short time.
Other issues The authors made appropriate comparisons of their findings with those from a similar study (Patterson et al., see Other Publications of Related Interest), which found results similar to those reported in this study. The issue of generalisability to other settings was partially addressed through the sensitivity analysis. The authors do not appear to have presented their results selectively. However, the lack of information on how the literature review was undertaken and how the authors used the results from the literature does not allow us to rule out the possibility of the results being used selectively. The authors' conclusions reflected the scope of the analysis.
The authors reported a further limitation to their study. They assumed, from the literature, that the prognosis of patients with negative SPECT results was more benign than that of patients with negative stress Echo results. However, the authors could not find any study in which the outcomes of these two technologies were compared. The authors stated that, to support such an assumption, appropriate studies should be designed and performed to compare the outcomes of both tests in the same patient population.
Implications of the study In their conclusions, the authors also noted that if the annual cardiac hard event rate of negative Echo decreased from 4 to 2% then a cheaper intervention, dobutamine Echo, would have become the most-cost effective option, mainly because of its lower price, similar performance and non diagnostic rate.
Bibliographic details Lee D S, Jang M J, Cheon G J, Chung J K, Lee M C. Comparison of the cost-effectiveness of stress myocardial SPECT and stress echocardiography in suspected coronary artery disease considering the prognostic value of false-negative results. Journal of Nuclear Cardiology 2002; 9(5): 515-522 Other publications of related interest Patterson RE, Eisner RL, Horowitz SF. Comparison of cost-effectiveness and utility of exercise ECG, single photon emission computed tomography, positron emission tomography, and coronary angiography for diagnosis of coronary artery disease. Circulation 1995;91:54-65.
Kim C, Kwok YS, Saha S, Redberg RF. Diagnosis of suspected coronary artery disease in women: a cost-effectiveness analysis. American Heart Journal 1999;137:1019-27.
Garber AM, Solomon NA. Cost-effectiveness of alternative test strategies for the diagnosis of coronary artery disease. Annals of Internal Medicine 1999;130:719-28.
Indexing Status Subject indexing assigned by NLM MeSH Coronary Angiography /economics; Coronary Artery Disease /diagnosis /economics; Cost-Benefit Analysis; Decision Trees; Echocardiography, Stress /economics; Exercise Test /economics; False Negative Reactions; Health Care Costs; Humans; Korea; Quality-Adjusted Life Years; Sensitivity and Specificity; Tomography, Emission-Computed, Single-Photon /economics AccessionNumber 22002001780 Date bibliographic record published 31/07/2004 Date abstract record published 31/07/2004 |
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