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Cost-effectiveness of primary implanted cardioverter defibrillator for sudden death prevention in congestive heart failure |
Chen L, Hay J W |
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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 investigated the use of implanted cardioverter defibrillators for preventing sudden death for congestive heart failure patients. This intervention was compared to conventional treatment, normally involving the use of beta-adrenoceptor blockers.
Study population The study population was a hypothetical population of newly diagnosed US CHF patients with New York Heart Association (NYHA) functional class II and III. These classes were chosen because patients in class I were not considered as having heart failure yet, while patients in class IV had rather high mortality and a lower chance of sudden death.
Setting The study setting was secondary care. The economic study was conducted at the University of Southern California, Los Angeles, USA.
Dates to which data relate Effectiveness data were derived fro studies published between 1986 and 2002. The resource use data were gathered from studies published between 1986 and 2002. The price year was 2002.
Source of effectiveness data Effectiveness data were obtained from a review and synthesis of previously completed studies, and were supplemented by several assumptions made by the authors.
Modelling A lifetime decision model was used by the authors to track a newly diagnosed CHF patient with NYHA Classification II or III.
Outcomes assessed in the review The outcomes assessed in the review were the annual all-cause mortality rate in the target population, the annual risk of CHF-related hospitalisation, the ICD operative death rate, the additional annual risks of hospital admissions, the base case utility of heart failure, the utility of survival within first year after implantation, and the rate of coronary artery disease in CHF patients, and who need to take aspirin and statins.
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 17 primary studies were included in the review, out of which, approximately seven were used to obtain utility values.
Methods of combining primary studies The authors did not report how the results obtained from multiple studies were combined together to derive the hospitalisation rate nor the utility of survival within first year after implantation.
Investigation of differences between primary studies The authors did not report any investigation of differences between primary studies.
Results of the review The annual all cause mortality rate in the target population was 20%, of which, 40% was due to pump failure, 40% was due to sudden death, and the remaining 20% was due to other causes.
The annual risk of CHF-related hospitalisation was 20%.
The ICD operative death rate was 1%.
The risk of CHF-related hospital admissions included: ICD-related infection (0.5%); ICD-related lead problems (dislodgement/fracture/migration) (8%); generator malfunction (1.9%); and system modification owing to threshold elevation (1.9%).
The base case utility of heart failure was 0.71.
The utility of survival within the first year after implantation was 0.639.
The proportion of patients who had coronary artery disease and needed to take aspirin and statins was 70%.
Methods used to derive estimates of effectiveness The authors supplemented the effectiveness data derived from the literature with their own assumptions, which were then incorporated into the decision model.
Estimates of effectiveness and key assumptions The authors made three basic assumptions:
(1) ICD would only prevent sudden death, and would not interfere with the progression or underlying mechanisms of CHF, nor would it change the prognosis of other non-cardiac diseases.
(2) the annual hazard of death is constant, and life expectancy is equal to the reciprocal of death hazard.
(3) ICD would fully prevent sudden death.
The authors also assumed that the ICD related adverse events were independent of each other, that ICD battery life is 5 years, and that there is a 5% annual reduction in utility for all CHF patients.
Measure of benefits used in the economic analysis The health benefits used in the economic analysis were quality-adjusted life-years (QALYs). Utility estimates were derived from the Beaver Dam health outcomes study and from a review of the literature.
Direct costs Resource use and costs were reported separately for some categories. The direct costs included in the analysis were those to the health care system, which included the costs of any medication, the costs for outpatient visits (i.e. GP visits and cardiologist) and tests (i.e. potassium/serum, serum urea nitrogen, creatinine/blood, digoxin test, ECG, Echocardiogram, and chest X-ray) and the costs for inpatient services. The quantities of resource use were derived from websites, literature and pharmacists. Drug costs were obtained from average wholesale prices from Red Book 2002. Information about outpatient management of CHF patients was obtained from a previously published study, with costs obtained from the CMS annual physician fee schedule and clinical lab fee schedule. CHF hospitalisation costs were derived from a previously published study, and the hospital costs for ICD implantation were obtained from DRG 2000, with DRG code 115 and relative weight 3.47. The base case annual discount rate was 3%, following accepted cost-effectiveness guidelines. The study reported average costs. All costs were converted to 2002 prices using the consumer price index.
Statistical analysis of costs Costs were treated as point estimates (i.e. the data were deterministic).
Indirect Costs The indirect costs were calculated as the value of time lost due to physician visits and hospital stays. Time lost due to physician visits and hospitalisation was derived from previously published studies. Average hourly wages and fringe benefits compensation were derived from the 2002 Bureau Labour Statistics.
Sensitivity analysis The authors performed one-way sensitivity analyses on all model parameters.
Estimated benefits used in the economic analysis 2.9301 QALYs were gained with primary prophylactic ICD and 1.9405 with conventional drug therapy.
Cost results The discounted lifetime costs were $122,947 with primary prophylactic ICD and $25,223 with conventional drug therapy.
Synthesis of costs and benefits A synthesis of costs and benefits was carried out by calculating a cost-utility ratio (i.e. the additional costs required per QALY gained). The incremental cost-utility ratio was $97,861 per QALY saved when prophylactic ICD was used over conventional treatment. The authors reported that they failed to demonstrate that the ICD in CHF patients was cost-effective under any plausible scenario investigated in the sensitivity analysis, using a $50,000-$80,000 per QALY saved threshold. The cost-utility ratio was found to be quite sensitive to patient utility after ICD implantation, the proportion of CHF patients experiencing sudden death and the cost of initial implantation.
Authors' conclusions The authors concluded that using a standard cost-effectiveness threshold of $50,000 per QALY, it was unlikely that implanted cardioverter defibrillators were cost-effective in preventing CHF sudden death relative to standard drug therapy.
CRD COMMENTARY - Selection of comparators A justification was given for using standard drug therapy as the comparator, namely that it represented current practice in the authors' organisations. You should decide if this is a widely used health intervention in your own setting.
Validity of estimate of measure of effectiveness The authors did not state that a systematic review of the literature had been undertaken to identify relevant research and minimise biases. When relevant, the authors did not report how estimates of effectiveness from the primary studies were combined. Furthermore, the authors did not provide any details of the methods used in the review. Hence, it would appear that the review was conducted in a selective fashion. To supplement the data from the review, the authors made some assumptions. Some of these assumptions were made with reference to the medical literature, but, as the authors report, the main assumption of the model that ICDs are 100% effective in preventing sudden death was simplistic and somewhat unrealistic. However, the authors used sensitivity analysis to test the effects of relaxing these assumptions.
Validity of estimate of measure of benefit The estimation of benefits was modelled. Utility values were obtained from the literature and related to studies of ICDs in varied samples. The authors acknowledged that the absence of utility estimates specific to heart failure patients treated with ICD limits the validity of the results, as sensitivity analysis showed that utility was a critical parameter.
Validity of estimate of costs All categories of cost relevant to the perspective adopted were included in the analysis. However, not all relevant costs were included in the analysis. For example, in the indirect costs, the authors did not include the productivity costs associated with sudden death. It would appear that the omission of these costs could bias the results in favour of standard therapy. Costs and quantities were reported separately for certain categories. Resource use was derived from published sources, and appropriate sensitivity analyses of quantities were performed. Unit costs were derived from published sources and DRGs. Again, appropriate sensitivity analyses were conducted. The price year was reported, which will assist any future reflation exercises. Since all costs were incurred over the lifetime of the patient, costs were appropriately discounted.
Other issues The authors did not clearly compare their results with those from other studies. In the introduction, however, the authors reported the results of three studies that provided favourable evidence of ICD cost-effectiveness in patients with reduced left ventricular function. However, none of these studies directly targeted CHF patients. The authors also reported the results of a study which questioned the value of primary prevention of sudden cardiac death in heart failure patients using a very simplified context. Nevertheless, this study also found that the estimated cost per life-year saved was above the $50,000 cost-effectiveness threshold. The issue of generalisability to other settings was partly addressed through the sensitivity analysis. The authors do not appear to have presented their results selectively, and their conclusions reflect the scope of the analysis. The authors reported three main limitations of their study. Firstly there were no utility estimates specific to ICD. Secondly, they assumed constant hazards for annual all-cause mortality and sudden death related mortality, although this assumption was appropriately relaxed in the sensitivity analysis. Lastly, they assumed that ICD treatment had no impact on CHF symptoms, although they noted that there was not much evidence to support or reject this assumption.
Implications of the study The authors did not make any explicit recommendations, but based on their results it would appear that the use of ICDs are not recommended in the prevention of sudden death in this population.
Bibliographic details Chen L, Hay J W. Cost-effectiveness of primary implanted cardioverter defibrillator for sudden death prevention in congestive heart failure. Cardiovascular Drugs and Therapy 2004; 18(2): 161-170 Other publications of related interest Mushlin AI, Hall WJ, Zwanziger J, et al. The cost-effectiveness of automatic implantable cardiac defibrillators: results from MADIT. Circulation 1998;9:2129-2135.
O'Brien BJ, Connolly SJ, Goeree R, et al. Cost-effectiveness of the implantable cardioverter-defibrillator: Results from the Canadian Implantable Defibrillator Study (CIDS). Circulation 2001;103(10):1416-1421.
Sheldon R, O'Brien BJ, Blackhouse G, et al. Effect of clinical risk stratification on cost-effectiveness of the implantable cardioverter-defibrillator: The Canadian Implantable Defibrillator Study. Circulation 2001;104(14):1622-1626.
Owens DK, Sanders GD, Harris RA, et al. Cost-effectiveness of implantable cardioverter defibrillators relative to amiodarone for prevention of sudden cardiac death. Annals of Internal Medicine 1997;126(1):1-18.
Indexing Status Subject indexing assigned by NLM MeSH Comorbidity; Cost-Benefit Analysis; Death, Sudden, Cardiac /etiology /prevention & Decision Making; Defibrillators, Implantable /economics; Economics, Pharmaceutical; Heart Failure /complications /economics /therapy; Humans; control AccessionNumber 22004000789 Date bibliographic record published 30/04/2005 Date abstract record published 30/04/2005 |
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