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Economic impact of the reduced incidence of atrial fibrillation in patients with heart failure treated with enalapril |
Wagner M, Rindress D, Desjardins B, Meilleur M C, Ducharme A, Tardif J 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 The study examined the impact of enalapril on the incidence of atrial fibrillation (AF) in patients with heart failure (HF).
Economic study type Cost-effectiveness analysis.
Study population The study population comprised a hypothetical cohort of patients with diagnosed asymptomatic to mild HF.
Setting The setting was secondary care. The economic study was carried out in Canada.
Dates to which data relate The effectiveness data were collected from studies published between 1991 and 2003. The resource use and cost data were derived from studies published from 1999 to 2003. The price year was 2004.
Source of effectiveness data The effectiveness evidence was derived from a synthesis of published studies.
Modelling A Markov model was developed to predict the costs and outcomes of reduced AF incidence with enalapril treatment over 5 and 10 years. One-year cycles were considered. The model included four health states:
initially, all patients were assumed to have no AF ("no AF state");
patients who developed AF moved to the "AF state";
patients who developed strokes and survived moved to the "poststroke state";
finally, a "death" state was considered.
The transition probabilities used in the model were derived from completed studies. The model assumed that most patients with AF would receive warfarin for stroke prevention.
Outcomes assessed in the review The outcomes assessed were:
the incidence of AF with and without enalapril treatment;
the incidence of stroke in patients with and without AF in the previous year, and after a previous stroke;
the proportion of strokes leading to death;
the incidence of major bleeding events with and without warfarin treatment;
the proportion of major bleeding events leading to death;
the all-cause mortality rates with and without enalapril treatment; and
the stroke risk reduction by warfarin.
Study designs and other criteria for inclusion in the review The impact of enalapril treatment on AF incidence was obtained from the SoLVD trial. The designs of the rest of the studies used to derive the model parameters were not reported.
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 At least 11 articles were included in the review.
Methods of combining primary studies The primary studies appear to have been combined using a narrative method.
Investigation of differences between primary studies The authors do not appear to have investigated differences between the primary studies.
Results of the review The incidence of AF was 0.019 with enalapril treatment and 0.083 without enalapril treatment.
The incidence of stroke was 0.045 in patients with AF in the previous year, and 0.02 in patients without AF in the previous year.
The incidence of stroke after a previous stroke was 0.059.
The proportion of strokes leading to death was 0.25.
The incidence of major bleeding events was 0.013 with warfarin treatment and 0.01 without warfarin treatment.
The proportion of major bleeding events leading to death was 0.2.
The all-cause mortality rate was 0.067 with enalapril treatment and 0.074 without enalapril treatment.
The stroke risk reduction by warfarin was 0.61.
Measure of benefits used in the economic analysis The summary measures of health benefit used were expected survival and the reduction in the incidence of AF. These were estimated by means of the model. The health benefits were not discounted.
Direct costs Discounting was applied at a rate of 3% since the costs were incurred during a time horizon longer than 2 years. The quantities of resource used and the costs were not presented separately for all items. The costs were obtained from the literature, mainly from Canadian studies. The costs of medication (warfarin and amiodarone), physician visits, laboratory tests, diagnostic procedures, hospitalisation, and some costs related to stroke (subacute inpatient care, home health and day care services) were included in the study. The cost of enalapril was not included in the model because it was administered to patients with HF, not with the purpose of preventing AF but for treating HF. The price year was 2004.
Statistical analysis of costs The costs were treated deterministically.
Indirect Costs The indirect costs were not included in the study.
Currency Canadian dollars (CAD). The conversion rate to US dollars ($) was $1 = CAD 1.37 in 1995/1996.
Sensitivity analysis One-way sensitivity analyses were carried out for the 5-year horizon to test the robustness of the results. The parameters tested were:
the incidence of AF,
the incidence of stroke,
the proportion of major bleeding events leading to death,
the all-cause mortality rates,
the proportion of AF patients treated with warfarin,
the stroke risk reduction by warfarin,
the proportion of AF patients hospitalised for AF,
the proportion of patients with HF with AF treated with amiodarone, and
the discount rate.
Most of the parameters were varied by +/- 10%. The cost of enalapril treatment was also considered in an additional analysis.
Estimated benefits used in the economic analysis Over the 5-year period, the average life expectancy was 4.18 years in the enalapril group and 4.11 years for patients not treated with enalapril. Sixty-nine per cent of patients in the enalapril group and 66.5% in the non enalapril-treated group were alive. The proportions of patients in the no AF state were 57.9% (enalapril) and 39.5% (no enalapril), respectively.
Over the 10-year period, the average life expectancy was 7.06 years in the enalapril group and 6.84 years for patients not treated with enalapril. The proportion of patients alive was 47.5% in the enalapril group and 44.1% in the non enalapril-treated group. The proportions of patients in the no AF state were 33.5% (enalapril) and 15.6% (no enalapril), respectively.
Cost results Over the 5-year period, the total costs per patient were CAD 9,656 in the enalapril group and CAD 10,039 in the non enalapril-treated group.
Over the 10-year period, the total costs per patient were CAD 17,125 in the enalapril group and CAD 17,650 in the non enalapril-treated group.
Synthesis of costs and benefits Patients receiving enalapril were less likely to die and to develop AF than those not receiving enalapril. Moreover, enalapril treatment resulted in savings per patient of CAD 383 over 5 years and CAD 525 over 10 years. Therefore, enalapril treatment was a dominant strategy and it was not necessary to calculate the incremental cost-effectiveness ratios.
The sensitivity analyses showed that the results were robust. They also demonstrated that enalapril became more cost-saving as the baseline risk for stroke in patients with AF increased and the use of warfarin decreased. Finally, additional analyses showed that if the cost of enalapril was included, the incremental cost in the enalapril treatment arm would be CAD 1,543 per patient over 5 years.
Authors' conclusions Patients with heart failure (HF) treated with enalapril incurred substantially lower costs over a 5- and 10-year horizon because of reduced morbidity associated with atrial fibrillation (AF).
CRD COMMENTARY - Selection of comparators Standard care, as defined in the SoLVD trials, was used as the comparator. This allowed the active value of enalapril to be evaluated. The reader's ability to understand the study and to generalise the results to their own setting would have been improved had the authors explicitly specified in the paper the exact nature of the standard care.
Validity of estimate of measure of effectiveness The effectiveness data came from published studies. It would appear that a systematic review of the literature was not undertaken and the search strategy was not reported. The methods used to extract and combine the primary estimates were not described. It should be borne in mind that some of the effectiveness estimations were derived from the SoLVD trials, which were conducted more than a decade before the economic analysis was performed, and that the treatment of HF has developed since the SoLVD study was performed. Nevertheless, the external validity of the model parameters was increased by including the key effectiveness items in the sensitivity analyses.
Validity of estimate of measure of benefit The summary measures of health benefit used in the model were appropriate as they captured the most relevant impacts of the interventions on patient health. Moreover, the use of survival allows comparison with the results of other studies. Discounting was not applied to the health benefits, even though most economic evaluation guidelines recommend it.
Validity of estimate of costs The perspective adopted in the study was stated and it seems that all the relevant categories of costs have been considered. The authors did not include the cost of enalapril in the base-case analysis, although a justification for this was provided. However, their justification does not appear relevant as enalapril was given in one group but not in the other. Therefore, there is a need to take the cost of enalapril into account, even if the primary purpose of enalapril was to treat HF. In addition, the sensitivity analysis showed that the cost-effectiveness analysis was sensitive to this parameter (enalapril treatment was no longer a dominant strategy, with an incremental cost of CAD 1,543 per patient over 5 years). Not all the quantities of resource used were reported, but an appropriate breakdown of the cost items was presented, thereby increasing the possibility of replicating the analysis in other settings. The price year and the sources of the costs were reported. The costs were adequately discounted. Sensitivity analyses included some of the cost items (by varying the probabilities of receiving different treatments).
Other issues The authors compared some of their findings with those of other studies that analysed enalapril as a treatment for patients with HF. No comparisons in the field of AF could be made since this was the first attempt to evaluate the economic impact of enalapril in the prevention of AF. The issue of generalisability to other settings was not addressed. Sensitivity analyses were undertaken only for the 5-year analyses. The authors did not justify why the 10-year results were not included in the sensitivity analyses.
Implications of the study The results of this study suggest that prescribing enalapril to reduce the incidence of AF in patients with HF could be effective and cost-saving on top of the already well-established benefits of enalapril for patients with HF.
Source of funding Funded by Merck Frosst Canada Ltd.
Bibliographic details Wagner M, Rindress D, Desjardins B, Meilleur M C, Ducharme A, Tardif J C. Economic impact of the reduced incidence of atrial fibrillation in patients with heart failure treated with enalapril. American Heart Journal 2005; 77(4): 150 Indexing Status Subject indexing assigned by NLM MeSH Absorption; Conservation of Natural Resources; Seasons; Soil; Texas; Volatilization; Waste Disposal, Fluid /methods; Water /chemistry AccessionNumber 22005001877 Date bibliographic record published 31/03/2007 Date abstract record published 31/03/2007 |
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