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Economic impact of an ultrasonographic contrast agent on the diagnosis and initial management of patients with suspected renal artery stenosis |
Levesque J, Lacourciere Y, Onrot J M, Wilson S R, Szaky E, Thibodeau M, Vasilevsky M L, Dashefsky S M, Allan D R, Lafortune M, Vendeville B, Zaleski W M, Page D E, D'Onofrio F |
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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 health technology studied was the use of contrast-enhanced duplex Doppler ultrasonography (CEDDUS) for the diagnosis of patients with suspected renal artery stenosis (RAS).
Economic study type Cost-effectiveness analysis.
Study population The study population comprised patients 18 years of age or older with suspected RAS (i.e. mainly patients having hypertension with resistance drug therapy).
Setting The setting was secondary care. The economic study was carried out in Canada.
Dates to which data relate The effectiveness data were from 1999 (reported in Lacourciere et al, see "Other Publications of Related Interest" below). The resource utilisation of the management pathways was projected. The price year was 1999.
Source of effectiveness data The effectiveness data was taken from a single study.
Link between effectiveness and cost data Costing appears to have been performed prospectively on the same patient population as that used for the effectiveness analysis.
Study sample No power calculations (to estimate a sample size that would assure a certain power) were reported in the planning phase of the study. 78 patients with a mean age of 53.1 years (range: 22 - 78) were included in the effectiveness analysis. The authors did not report that the study sample was representative of the study population. Additional information on the study sample was given in Lacourciere et al.
Study design This was a prospective diagnostic cohort study. The 78 patients were their own controls since both CEDDUS and one of the comparators were used for diagnosis in all patients across the seven centres. The comparators were either CERS (performed at six of the seven centres) or RUUS (performed at one centre). The duration of follow-up was three months. There was no loss to follow-up. The authors reported that the investigator at each centre was blinded to the results of the CEDDUS test until the CERS or RUUS results were reported, and the management strategy for each patient was planned according to the results of each of the diagnostic tests.
Analysis of effectiveness All the patients included in the study were accounted for in the analysis. The primary health outcomes used in the effectiveness analysis were: the number of patients that could be conclusively diagnosed with either normal (i.e. clinically non-significant stenosis) or significant stenosis by means of either CEDDUS, or the comparator (CERS or RUUS), and the number of patients with normal or significant stenosis for whom the diagnosis was identical with the two diagnostic procedures. The diagnostic success rates (i.e. the ability of the tests to provide a definitive diagnosis) for CEDDUS, and CERS or RUUS, were also reported. It was not necessary to show that the groups were comparable at analysis since the same group was used as both the intervention and the control group.
Effectiveness results With CEDDUS, 65 patients were diagnosed with normal stenosis, 9 with significant stenosis, and only one patient received an inconclusive diagnosis.
With either CERS or RUUS, 56 patients were diagnosed with normal stenosis, 8 with significant stenosis, and 14 could not be conclusively diagnosed.
The diagnostic success rates were: 99% for CEDDUS, and 82% for CERS or RUUS.
Clinical conclusions The number of conclusive diagnoses of RAS was higher using the CEDDUS method.
Measure of benefits used in the economic analysis The summary measure of benefit used in the economic study was the number of conclusive diagnoses obtained by each of the alternatives considered at analysis.
Direct costs There were 2 costing analyses in this study. The first, used in an economic analysis, incorporated the cost of diagnostic tests and the costs of workdays lost by employed patients and leisure time lost by all patients in order to undergo those tests (see indirect costs below). No patient out of pocket costs were included.
The second analysis measured resource consumption based on planned and recommended management pathways (PMP & RMP). The investigator derived the planned pathway on the basis of the CERS or RUUS diagnostic test results. Once the CEDDUS test had been completed, a recommended management pathway was developed using input from both test results. Actual resource consumption was also recorded during follow-up. To what degree the results of the usual test influenced the recommended pathway was not clear. However, the authors attempted to infer cost implications from using one test rather than the other. This cost analysis excluded the costs in the first analysis.
The direct costs considered in the second analysis were those of the health service, and included hospital admissions, medical consultations, diagnostic and laboratory tests (including further angiography for those CEDDUS, CERS or RUUS results that were not conclusive), surgical procedures, and new medications. From the perspective of the Ministry of Health, the medication costs were not included (although these costs were included in the overall calculation of the final cost from a societal perspective). The sources of the unit costs were the Ontario Schedule of Benefits for Physician Services, average costs from several teaching hospitals in Ontario, and the Ontario Drug Benefit Formulary database. Discounting was not performed, which was appropriate as the period of follow-up was three months. Most of the resource quantities and costs were reported separately. The study reported average costs per patient. The price year stated was 1999.
Statistical analysis of costs Descriptive statistics were reported.
Indirect Costs Productivity losses (considering both work days and leisure time lost because of attending for the diagnostic tests) were included in the economic analysis to take account of a societal perspective. The source of the indirect costs was a follow-up interview, which was conducted 3 months after treatment began. Resource quantities and costs were reported separately. The average daily Canadian salary and the minimum wage, taken from Statistics Canada, were used as sources of the indirect costs. Therefore, the estimation of quantities and costs was based on actual data. The price year was 1999. Appropriately, as the study period was only three months, discounting was not performed.
Sensitivity analysis The authors stated that sensitivity analyses were performed to test the robustness of the results. The unit costs of the diagnostic tests, surgical procedures and new medications were modified by 20% in either direction. Therefore, the area of uncertainty investigated was variability in cost data. The authors did not report the method used to perform the sensitivity analyses.
Estimated benefits used in the economic analysis The reader is referred to the "Effectiveness results" reported earlier.
Cost results The total cost of the CEDDUS diagnostic method was Can$300 per patient (standard deviation = 10), while the total cost for the conventional diagnostic method (CERS or RUUS) was Can$292 per patient (standard deviation = 98).
The 3-month follow-up costs for the planned and recommended management pathways (see "Direct costs" above) were Can$219 (standard deviation = 412) for RMP, and Can$130 (standard deviation = 270) for PMP, from the Ministry of Health (MoH) perspective. Follow-up costs were Can$294 (standard deviation = 491) for RMP, and Can$227 (standard deviation = 377) for PMP, from the societal perspective (including new medications).
The actual costs of treatment reported were Can$287 (standard deviation = 679) under an MoH perspective, and Can$360 (standard deviation = 747) under a societal perspective.
The reported costs did not include adverse effects since the authors stated that there were no adverse effects in the effectiveness analysis.
The costs by subgroups of patients (i.e. normal stenosis patients, significant stenosis patients and patients with inconclusive results) were also reported.
Synthesis of costs and benefits Estimated benefits and costs were combined using cost-effectiveness ratios (CERs) that calculated the cost of the diagnostic method per patient with a conclusive diagnosis. The CERs were Can$343 per conclusive diagnosed patient with CEDDUS, and Can$422 per conclusive diagnosed patient with either CERS or RUUS. (See 'Direct costs' above for the costs included).
The authors noted that the results of the sensitive analyses showed little variations in the results, with the costs of the diagnostic procedures as the most sensitive parameters, influencing in particular the subgroup of patients with conflicting diagnostic results.
Authors' conclusions The authors concluded that the study demonstrated that CEDDUS is more effective than the conventional diagnostic tests for RAS, and is associated with potential costs savings derived not only from the application of the test itself but also from lower consumption of medical resources associated with patients whose diagnosis was unclear following usual diagnostic tests.
CRD COMMENTARY - Selection of comparators A justification was given for the comparators used, namely that CEERS and RUUS were the usual diagnostic procedures used in the authors' setting. However, there are other tests and, as the user of this database, you must decide whether these are widely used health technologies in your own setting.
Validity of estimate of measure of effectiveness The analysis was based on a prospective diagnostic study. The measure of effectiveness was the percentage of patients that could be diagnosed by either test. The possibility exists that the results were due to chance as the sample size was low. There is also a possibility of selection bias as the authors did not show evidence that the study sample was representative of the study population. However, the fact that seven sites were included in the analysis may have increased the likelihood that this study sample was representative. The authors of the original paper noted that there was a possibility of performance bias because all ultrasound examinations were first performed without contrast agent. This might have favoured the outcome of enhanced ultrasound since the radiologists had an opportunity to locate the area of interest and correctly position the probe on areas that were difficult to image.
The possibility of confounding was low as the same patient sample was tested by both diagnostic methods.
Although CEDDUS presented better performance in terms of the diagnostic success rate, in terms of the number of conclusive diagnoses, the authors did not report how many false positive and false negative results there were among the patients diagnosed by CEDDUS.
Validity of estimate of measure of benefit The estimation of benefits (in terms of the number of conclusive diagnoses with each of the diagnostic alternatives considered) was obtained directly from the effectiveness analysis. This choice of estimate was justified because it has been used as a common measure of health benefit in the economic evaluations of the RAS diagnostic tests. However, as the authors stated, other measures of health benefits have been used in studies of diagnostic strategies for RAS, such as cost per year of life gained.
Validity of estimate of costs The follow-up costs were excluded in the economic analysis. The follow-up health service costs were projected from patient management pathways developed by the investigator on review of the diagnostic results. It was unclear if the 2 pathways developed reflected the 2 types of testing as alternatives or whether the recommended pathway was a result of both tests. The authors stated that the true costs of the resources used may have been underestimated. Furthermore, the great variance in actual costs from the projected costs calls into question the validity of the projected costs, even though the costing was not exactly the same for the two estimates. The authors tried to address the uncertainty in the costs by performing sensitivity analyses.
There was some breakdown of quantities and unit costs and the price year was stated. These factors facilitate potential reflation exercises to other settings. Discounting was not performed, but this was appropriate as the period considered at analysis was less than two years. Overall, the validity of the costing was lo
Other issues The authors compared their cost findings with those from other studies, which supported the finding of lower costs for CEDDUS when compared to the conventional diagnostic methods. The issue of the generalisability of the results to other settings was not addressed. The authors' conclusions reflected the scope of the analysis.
Implications of the study The results of the study showed that CEDDUS was more effective and may be potentially cost saving when compared to the other usual diagnostic procedures evaluated. However, the discussion above suggests the need for caution in the interpretation of these results.
Source of funding Grant from Berlex Canada Inc.
Bibliographic details Levesque J, Lacourciere Y, Onrot J M, Wilson S R, Szaky E, Thibodeau M, Vasilevsky M L, Dashefsky S M, Allan D R, Lafortune M, Vendeville B, Zaleski W M, Page D E, D'Onofrio F. Economic impact of an ultrasonographic contrast agent on the diagnosis and initial management of patients with suspected renal artery stenosis. Canadian Association of Radiologists Journal 2002; 53(4): 228-236 Other publications of related interest Blaufox D M, Middleton M L, Bongiovanni J, Davis B R. Cost efficacy of the diagnosis and therapy of renovascular hypertension. Journal of Nuclear Medicine 1996;37:171-177.
England W L, Grim C E, Weinberger M H, Roberts S D. Cost effectiveness in the detection of renal artery stenosis. Journal of General Internal Medicine 1988;3:344-50.
Lacourciere Y, Levesque J, Cooperberg PL, Onrot JM, Wilson SR, Szaky E, et al. Impact of Levovist ultrasonographic contrast agent on the diagnosis and management of hypertensive patients with suspected renal artery stenosis: a Canadian multicentre pilot study. Canadian Association of Radiologists Journal 2002;53:219-227.
McNeil B J, Varady P D, Burrows B A, Adelstein SJ. Cost-effectiveness calculations in the diagnosis and treatment of hypertensive renovascular disease. New England Journal of Medicine 1975;293:216-21.
Nelemans P J, Kessels A G H, De Leeuw P, De Haan M, van Engelshoven J. The cost-effectiveness of the diagnosis of renal artery stenosis. European Journal of Radiology 1998;27:95-107.
Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Contrast Media /economics; Cost-Benefit Analysis; Female; Humans; Hypertension, Renovascular /etiology; Male; Middle Aged; Renal Artery Obstruction /complications /ultrasonography; Ultrasonography, Doppler, Duplex /economics AccessionNumber 22002001893 Date bibliographic record published 31/10/2003 Date abstract record published 31/10/2003 |
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