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Cost-effectiveness of spironolactone in patients with severe heart failure |
Tilson L, McGowan B, Ryan M, Barry M |
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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 use of spironolactone (mean daily dose 25 mg) in combination with standard therapy was investigated in patients with severe heart failure. Standard therapy could include a loop diuretic, an angiotensin-converting enzyme inhibitor, digoxin, a beta-blocker, or a combination of these.
Economic study type Cost-effectiveness analysis.
Study population The study population comprised a hypothetical cohort of patients with severe heart failure (defined as NYHA Class III and IV; left ventricular ejection fraction <= 35%), aged 65 years on average.
Setting The setting was secondary and tertiary care. The economic study was conducted at the National Centre for Pharmacoeconomics, St. James's Hospital, Dublin, Ireland.
Dates to which data relate The effectiveness and resource use data were obtained from studies published between 1999 and 2001. The price years appear to have been 2000-2001 and 2001-2002.
Source of effectiveness data The effectiveness data were derived from a review of published studies, which did not seem to have been conducted systematically.
Modelling The study was performed through the design of a Markov model. Three health states were defined. These were severe heart failure, severe heart failure with hospitalisation, and death. The model was run over a 10-year period and the cycle length was 1 year.
Outcomes assessed in the review The outcomes assessed were:
the probabilities of mortality and hospitalisation for patients treated with spironolactone plus standard therapy; and
the probabilities of death and hospitalisation for patients on standard therapy.
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 Two studies were included in the review. The probabilities for death and hospitalisation for patients on standard therapy were obtained from a cohort of patients attending the authors' hospital over a 12-month period (McGowan et al., see Other Publications of Related Interest). The differences in the probabilities of mortality and hospitalisation for patients treated with spironolactone plus standard therapy were obtained from the randomised Aldactone evaluation (RALES) study (Pitt et al., see Other Publications of Related Interest).
Methods of combining primary studies Investigation of differences between primary studies Results of the review For patients treated with standard therapy alone, the probability of death was 0.26 and the probability of hospitalisation due to severe heart failure was 0.38.
For patients treated with spironolactone plus standard therapy, the probability of death was 0.18 and the probability of hospitalisation due to severe heart failure was 0.25.
Methods used to derive estimates of effectiveness The authors made an assumption in their model.
Estimates of effectiveness and key assumptions The authors assumed that the probabilities of hospitalisation and death for severe heart failure among patients on spironolactone would revert to those of patients receiving standard therapy after the trial period of 2 years (which was the mean follow-up period of the RALES study).
Measure of benefits used in the economic analysis The measure of benefits used was the life-years gained (LYG). These may have been obtained directly from the reviewed studies. The time horizon considered for the estimation of benefits was 2 years, and a discount rate of 1.5% was applied.
Direct costs The resource use quantities and costs were not reported separately. The direct costs included in the analysis were those of the hospital. These comprised the drug acquisition cost of spironolactone, the cost of hospitalisation for the treatment of severe heart failure, and the cost of outpatient clinic visits. Drug costs were obtained from the Irish Monthly Index of Medical Specialities (July 2002 edition). The drug costs were not subjected to any adjustment. The cost of hospitalisation and outpatient visits were obtained from a published study that had been performed in the authors' setting. Therefore, the costs were estimated from actual data. Discounting was necessary, as the costs were incurred during 10 years, and was appropriately performed at a rate of 5% per annum. The authors did not report the total cost associated with any of the two treatment arms, reporting instead the incremental costs of adding spironolactone to standard therapy. The costs were inflated to 2000-2001 (5.6%) and 2001-2002 (4.9%) prices using the annual Consumer Price Index, as provided by the Central Statistics Office.
Statistical analysis of costs The costs were treated as point estimates (i.e. the data were deterministic).
Indirect Costs The indirect costs were not included.
Currency Euros (Euro). The costs were originally obtained in Irish pounds then converted into Euros. The authors did not report the exchange rate used.
Sensitivity analysis A series of one- and two-way sensitivity analyses were undertaken to investigate uncertainty related to variability in the data. The parameters modified were the hospitalisation and mortality rates (based on 95% confidence intervals from the RALES study), the number of required outpatient visits, and the costs of hospitalisation (based on the ranges observed in a published study).
Estimated benefits used in the economic analysis The authors did not report either the LYG in each treatment arm, or the incremental number of LYG by adding spironolactone to standard therapy in comparison with standard therapy alone.
Cost results The authors did not report the total cost associated with any of the two treatment arms, only the incremental costs incurred when adding spironolactone to the standard practice.
Synthesis of costs and benefits The costs and benefits were combined using an incremental cost-effectiveness ratio (estimated as the added cost incurred per each additional LYG by adding spironolactone to standard therapy, compared with standard therapy alone). In this study, the incremental cost-effectiveness ratio of spironolactone in patients with severe heart failure was Euro 466 per LYG.
The sensitivity analyses demonstrated that the results of the model were sensitive to changes in hospitalisation and mortality rates, and to variations in the cost of hospitalisation and outpatient visits. However, the incremental cost-effectiveness was maintained in the range of Euro 75 to Euro 1,136 per LYG, which the authors considered to be cost-effective.
Authors' conclusions The addition of spironolactone to standard therapy was highly cost-effective in the treatment of severe chronic heart failure.
CRD COMMENTARY - Selection of comparators A justification was given for the comparator used. It represented current practice in the authors' settings. You should decide if the comparator represents current practice in your own setting.
Validity of estimate of measure of effectiveness It appears that a systematic review of the literature was not performed to identify relevant research and minimise biases, as only two studies were included in the review. The authors used data from two studies with follow-up periods of 1 and 2 years, and extrapolated these results to a 10-year period, which may not have been appropriate in this simple model. Even though the authors performed a sensitivity analysis of the effectiveness of spironolactone combined with standard therapy, they did not perform a sensitivity analysis on the rates of hospitalisation and mortality in patients treated with standard therapy alone.
Validity of estimate of measure of benefit The estimation of benefits was modelled using a Markov model. However, the authors failed to report the number of LYG in each of the two treatment arms, which will limit the validity of the model and the generalisability of the authors' results. As benefits could be incurred during a 10-year period, the future outcomes were discounted at a rate of 1.5% per annum. A more appropriate measure of benefit would have been the number of quality-adjusted life-years gained, as it would permit comparison of the achieved health benefits across interventions of a different nature. However, as the authors stated, this measure of benefit was not considered because of the lack of available data.
Validity of estimate of costs The authors failed to report the perspective used in the economic analysis, so it is unclear whether all the appropriate cost categories were included. Moreover, as the authors did not report the costs included in much detail, it remains unclear whether all the relevant costs were included in the analysis. The costs and the quantities were not reported separately, which will limit the generalisability of the authors' results. The costs were obtained from the authors' settings and from published sources. Although the authors performed sensitivity analyses on the costs of hospitalisation and the number of outpatient visits required, they failed to vary the drug costs and outpatient visit costs. Hence, the sensitivity analysis may not have been sufficiently comprehensive. Discounting was necessary, as the costs were incurred during 10 years, and was appropriately performed. The price year was reported, which will aid any future inflation exercises.
Other issues The authors made appropriate comparisons of their findings with those from other studies. A cost-effectiveness study from Spain, which used data from the RALES study, demonstrated that spironolactone was also cost-effective, albeit the incremental cost-effectiveness ratio was higher (Euro 3,555 per LYG) because it considered a wider perspective (i.e. a societal perspective). The authors do not appear to have presented their results selectively. However, the model used would appear to be too simplistic to be able to determine the cost-effectiveness of spironolactone over a 10-year period. The authors did not report any limitations to their study.
Implications of the study From their results and conclusions, the authors would appear to recommend the use of spironolactone in combination with standard therapy in the Irish health care setting, as it was found to be highly cost-effective.
Bibliographic details Tilson L, McGowan B, Ryan M, Barry M. Cost-effectiveness of spironolactone in patients with severe heart failure. Irish Journal of Medical Science 2003; 172(2): 70-72 Other publications of related interest McGowan B, Heerey A, Ryan M, et al. Cost of treating heart failure in an Irish teaching hospital. Irish Journal of Medical Science 2001;169:241-4.
Pitt B, Zannad F, Remme WJ, et al. The effect of spironolactone on morbidity and mortality in patients with severe heart failure (RALES). New England Journal of Medicine 1999;341:709-17.
Soto-Alvarez J, Gonzalez-Vilchez F. Cost effectiveness of the use of spironolactone in the treatment of chronic heart failure. Anales de Medicina Interna 2001;18:421-5.
Barry M. Cost-effectiveness of beta blocker therapy for patients with chronic severe heart failure. Irish Medical Journal 2002;95:174-7.
Indexing Status Subject indexing assigned by NLM MeSH Cost-Benefit Analysis; Costs and Cost Analysis; Heart Failure /drug therapy; Humans; Markov Chains; Mineralocorticoid Receptor Antagonists /economics /therapeutic use; Spironolactone /economics /therapeutic use AccessionNumber 22003001159 Date bibliographic record published 31/05/2005 Date abstract record published 31/05/2005 |
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