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Economic and clinical impact of alternative disease management strategies for secondary prevention in type 2 diabetes in the Swiss setting |
Gozzoli V, Palmer A J, Brandt A, Spinas G A |
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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 various interventions for the management of Type 2 diabetes (non insulin dependent; hereafter, referred to as diabetes).
Economic study type Cost-effectiveness analysis.
Study population The study population comprised a simulated cohort to represent the Swiss Type 2 diabetes population. The cohort had the following profile: age, 63 years; 46.4% women; duration of diabetes, 13 years; haemoglobin(Hb) A1c, 7.4%; arterial hypertension, 16.9%; total cholesterol, 6.0 mmol/L; high-density lipoprotein cholesterol, 1.01 mmol/L; triglycerides, 2.46 mmol/L; smokers, 15.4%; RS, 75.2%; NS, 15.5%; proliferative retinopathy, 14.4%; microalbuminuria, 17.2%; macroalbuminuria, 10.2%; end-stage renal disease, 5.5%; history of acute myocardial infarction, 9.8%; history of stroke, 5.7%; history of amputation, 3.0%. The same simulated cohort was subjected to each of the different interventions.
Setting The setting was primary care. The economic study was carried out in Switzerland.
Dates to which data relate The effectiveness evidence was derived from studies published from 1991 to 1999. The resources use data were from studies published from 1994 to 1997. The price year was 1996.
Source of effectiveness data The effectiveness data were derived from a review or synthesis of completed studies
Modelling A Markov model was used to simulate the clinical and economic implications of six diabetes-related short- and long-term complications for a cohort of the Swiss Type 2 diabetes population. The complications were hypoglycaemia, nephropathy, retinopathy, acute myocardial infarction, stroke and amputation) for a cohort of the Swiss Type 2 diabetes population. The model assessed the cost-effectiveness of the alternative management strategies. Follow-up was over the life of all patients in the cohort (30 years). Full details of the model were published elsewhere (see Other Publications of Related Interest).
Outcomes assessed in the review The outcomes assessed were HbA1c level, lipids, blood pressure and nicotine abuse. These represented the short-term effects of the interventions on clinical variables. The review also included general mortality data, and event probabilities that were derived from non-Swiss literature.
Study designs and other criteria for inclusion in the review The review included mostly observational, uncontrolled studies plus one randomised controlled trial. The general mortality data for the Swiss population were derived from published mortality tables.
Sources searched to identify primary studies MEDLINE was searched. No further details were provided.
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 A total of 15 studies were used to derive the effectiveness and epidemiological data used in the model.
Methods of combining primary studies Data on the effectiveness of the interventions were obtained from weighted averages of the results from observational studies. There was no indication of how the weighting was applied.
Investigation of differences between primary studies Results of the review It was assumed that the educational programme would be repeated every 5 years, and that it reduced the HbA1c level by 1.3% (absolute reduction) and the proportion of smokers by 25% (relative reduction).
It was assumed from the literature that the multifactorial intervention reduced the HbA1c by 1.6% (absolute reduction), the systolic blood pressure by 9 mmHg, the total cholesterol by 0.23 mmol/L (9 mg/dL), and the proportion of smokers by 25% (relative reduction).
The percentage reductions in the cumulative event rate for major diabetic complications were reported for the multifactorial intervention, compared with standard care. The reductions were -3.89% for acute myocardial infarction, -24.43% for amputation, -5.15% for stroke, -26.7% for blindness, and -53.01 for end-stage renal failure.
Measure of benefits used in the economic analysis Mean life expectancy of the simulation cohort was the outcome measure used in the economic analysis. The results were reported for a 0, 3 and 5% annual discount rate.
Direct costs Discounting was applied to costs using rates of 0, 3 and 5%. The quantities and the costs were not analysed separately. The overall costs for the intervention elements and the treatment of complications were reported for the event and first year, and for the following years, for fifteen categories. The categories were diabetes standard care, educational programme, multifactorial interventions, NS, ACE-inhibitor therapy, RS, photocoagulation, acute myocardial infarction, stroke, amputation, haemodialysis, peritoneal dialysis, kidney transplantation, blindness, and hypoglycaemia.
The cost data were obtained from published studies and from the authors' own calculations. The price year used was 1996. The authors reported the mean total and incremental costs for each strategy. All the relevant costs for the intervention being modelled were included in each simulation.
Statistical analysis of costs The costs were not treated in a stochastic way. Variability in the data was handled, appropriately, in the sensitivity analyses.
Indirect Costs The indirect costs were not included in the analysis.
Sensitivity analysis A series of one-way sensitivity analyses was performed. All probabilities and cost estimates used in the model were varied by +/- 10% to investigate uncertainty in the variability of the model data.
Estimated benefits used in the economic analysis The 3% discount rate results for life expectancy were:
for standard care, 8.81;
for standard care plus EP, 8.87;
for standard care plus EP plus NS, 9.04;
for standard care plus EP plus NS plus RS, 9.04; and
for the multifactorial intervention, 9.17.
Cost results The mean total lifetime costs at a 3% discount rate were:
for standard care (comparator), Sfr 68,418;
for EP, Sfr 68,573;
for EP plus NS, Sfr 61,156;
for EP plus NS plus RS, Sfr 61,446; and
for the multifactorial intervention, Sfr 61,105.
Since the treatments resulted in reduced cost-intensive complications, with the exception of the educational programme, the average total lifetime costs of the interventions were lower than that of the comparator (standard care).
Synthesis of costs and benefits The costs and the benefits were not combined. With the exception of the educational programme, all of the interventions dominated the comparator since the costs were lower and the life expectancy higher.
The results were presented as extrapolated annual cumulative savings of each intervention over standard care, as applied to the Swiss Type 2 diabetes population (285,000 patients, 3.5% prevalence).
The annual savings over standard care were:
for the educational programme, Sfr -4.1 million;
for EP plus NS plus RS, Sfr 185 million;
for EP plus NS, Sfr 193 million; and
for the multifactorial intervention, Sfr 194 million.
In the sensitivity analysis, the most marked impact on life expectancy was the incidence of myocardial infarction (life expectancy 11.23 to 11.35 for the multifactorial intervention) and end-stage renal disease (life expectancy 11.27 to 11.31 for the multifactorial intervention). The cost elements with the strongest influence on the average total lifetime cost were the annual costs for haemodialysis (total lifetime costs of 59,626 to 66,374 for the multifactorial intervention) and the treatment of diabetes (total lifetime costs of 59,691 to 62,518 for the multifactorial intervention)
Authors' conclusions The cost-effectiveness analysis of different disease management strategies in patients with Type 2 diabetes suggested that, compared with standard care, their implementation may lead to an improvement in the life expectancy and a reduction in the total lifetime costs. In the simulation, the improved control of cardiovascular risk factors (blood glucose, lipids, blood pressure and smoking status), combined with the early diagnosis and treatment of diabetic complications, led to an improvement in undiscounted life expectancy (0.56 years) and a reduction of in the total lifetime costs (10.7% per patient).
CRD COMMENTARY - Selection of comparators The selection of the comparator was not explicitly justified. However, it was the current practice in the Swiss setting and was, therefore, appropriate.
Validity of estimate of measure of benefit The estimation of the benefits was appropriately modelled, on the basis of the effects of interventions reported mainly in uncontrolled observational studies and one randomised controlled trial. MEDLINE was searched for relevant studies, but more details of the search criteria would have been helpful in terms of objectively appraising the validity of the studies used in the analysis. The event probabilities were derived from studies originating in other countries, therefore, there is the potential for variations in relation to the Swiss population. The authors acknowledge the limitations of the effectiveness data used, and the weighted averages approach to derive point estimates for the model (as opposed to meta-analyses). The Markov model used to generate the average life expectancy benefits, and to synthesise the costs and the benefits over the lifetime of the studied population, taking into account health state transitions, was appropriate. Details of the model were published elsewhere (see Other Publications of Related Interest).
Validity of estimate of costs The costs were estimated from the perspective of a health insurance payer. All major relevant costs were included in the model and a single price year was given. The resource usage and costs for each intervention were appropriately provided, based on average values.
Other issues The authors compared their results with similar studies obtained for the management of Type 1 diabetes. The issue of generalisability to settings other than Switzerland was not explicitly addressed. The model only considered some aspects of diabetes and a selection of specific treatments. The authors acknowledged that other complications, such as diabetic neuropathy, diabetic foot syndrome, and diabetes-related infections were not considered in the model. In addition, the economic analysis did not examine the costs from a societal perspective, which would have been appropriate for the patient domain studied. However, the authors argued that since the interventions examined the results in terms of the reduction of complications with high morbidity, such as end-stage renal failure, they will also lead to a reduction in the indirect costs.
Implications of the study The authors consider that their study adds to the growing evidence that optimised diabetes care offers improved health outcomes and may be financed by the complication costs avoided.
Bibliographic details Gozzoli V, Palmer A J, Brandt A, Spinas G A. Economic and clinical impact of alternative disease management strategies for secondary prevention in type 2 diabetes in the Swiss setting. Swiss Medical Weekly 2001; 131(21-22): 303-310 Other publications of related interest Palmer AJ, Weiss C, Sendi P P, Neeser K, Brandt A, Singh, et al. The cost-effectiveness of different management strategies for type 1 diabetes: a Swiss perspective. Diabetologia 2000;43:13-26.
Indexing Status Subject indexing assigned by NLM MeSH Complementary Therapies; Cost of Illness; Cost-Benefit Analysis; Diabetes Mellitus, Type 2 /economics /prevention & Disease Management; Female; Humans; Life Expectancy; Male; Middle Aged; Patient Education as Topic; Risk Factors; Switzerland /epidemiology; control /therapy AccessionNumber 22001001531 Date bibliographic record published 31/12/2002 Date abstract record published 31/12/2002 |
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