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Lifetime health consequences and cost-effectiveness of rosiglitazone in combination with metformin for the treatment of type 2 diabetes in Spain |
Shearer A T, Bagust A, Ampudia-Blasco F J, Alvarez B M, Escolano E P, Paris G |
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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 rosiglitazone (ROS) in combination with metformin (MET) for the treatment of Type 2 diabetes in obese or overweight patients. ROS was given at a dose of 4 mg once daily (titrated to twice daily) in combination with MET (850 mg twice daily), after the failure of MET monotherapy.
Economic study type Cost-effectiveness analysis and cost-utility analysis.
Study population The study population comprised a hypothetical cohort of obese and overweight patients aged older than 20 years, with Type 2 diabetes, who failed to control hyperglycaemia with MET monotherapy.
Setting The setting was secondary care. The economic study was carried out in Spain.
Dates to which data relate The effectiveness data were derived from studies published between 1995 and 2006. Resource consumption came from databases that were searched for economic data in 2003. The price year was 2002.
Source of effectiveness data The effectiveness data were derived from a synthesis of published studies.
Modelling The DiDACT is a long-term economic model of disease progression and health care resource consumption for individuals with Type 2 diabetes. The original model was slightly modified to reflect Spanish treatment patterns and updated epidemiological trends. The three main objectives of the model were:
to characterise the lifetime experience of diabetes-related morbidities and resource use for individuals with Type 2 diabetes;
to estimate the expected health outcomes and costs; and
to provide a basis for the evaluation of alternative treatments available for individuals with Type 2 diabetes.
The model consisted of a series of interconnected Markov models. The model included the possible complications for individuals with Type 2 diabetes, such as coronary heart disease (CHD), stroke, microalbuminuria, proteinuria, neuropathy, peripheral vascular disease and background diabetic retinopathy. No other details of the model were given.
Outcomes assessed in the review The outcomes estimated from the literature were:
international age- and gender-specific incidence rates of diabetes,
the Spanish population profile,
the transition probabilities across health states,
the prevalence of complications (CHD, stroke, microalbuminuria, proteinuria, neuropathy, peripheral vascular disease and background diabetic retinopathy),
Spanish age-, gender-, and cause-specific mortality rates,
Spanish census population data, and
treatment effectiveness.
Study designs and other criteria for inclusion in the review The primary studies appear to have been identified selectively, and a review of the literature does not appear to have been carried out. Some data came from administrative databases, but details on the majority of the primary studies 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 Eleven primary studies provided the clinical data.
Methods of combining primary studies The primary estimates were not combined since each study was used to derive a series of clinical estimates.
Investigation of differences between primary studies Results of the review The rates of complications were 16.5% for CHD, 4% for stroke, 15.1% for microalbuminuria, 2.2% for proteinuria, 15% for neuropathy, 12% for peripheral vascular disease and 10% for background diabetic retinopathy.
Twenty-five per cent of patients on ROS required complementary lipid-lowering therapy with simvastatin.
Other clinical estimates used in the model were not reported.
Measure of benefits used in the economic analysis The summary benefit measures used were the life-years (LYs) and quality-adjusted life-years (QALYs). These were estimated using a modelling approach. The utility weights used to assess QALYs were obtained from a published study that used the time trade-off method. An annual discount rate of 5% was applied to the benefits. Some model outputs, including insulin initiation years from diagnosis, incidence of CHD, clinical nephropathy and severe visual loss, were also reported.
Direct costs The analysis of the costs was conducted from the perspective of the SNS. The cost categories included were inpatient, outpatient, primary care, diabetes medication and other medications. The unit costs were presented for most items, whereas the quantities of resources used were reported for only a few items. The costs were estimated using data derived from a Spanish database and average retail prices. The estimation of drug costs took the co-payment share into account. The resource use data were derived from Spanish databases and some authors' assumptions. Discounting was relevant, given the lifetime time horizon of the model, and an annual rate of 5% was used. All costs were converted into 2002 values using the Spanish Consumer Price Index.
Statistical analysis of costs The costs were treated deterministically.
Indirect Costs The indirect costs were not considered in the economic evaluation.
Sensitivity analysis A series of univariate sensitivity analyses was carried out to assess the robustness of the cost-effectiveness and cost-utility ratios to variations in the discount rate, number of outpatient visits, number of primary care visits, and non-diabetes medications. The authors selected the alternative values.
Estimated benefits used in the economic analysis The model projected that MET monotherapy failed after approximately 10 years and was then followed by ROS+MET, MET+SUL or MET+INS.
In a hypothetical cohort of 1,000 overweight patients, the discounted LYs gained with ROS+MET were 85 in comparison with MET+SUL and 63 in comparison with MET+INS. The discounted QALYs gained with ROS+MET were, respectively, 124 (versus MET+SUL) and 169 (versus MET+INS).
In a hypothetical cohort of 1,000 obese patients, the discounted LYs gained with ROS+MET were 73 in comparison with MET+SUL and 51 in comparison with MET+INS. The discounted QALYs gained with ROS+MET were, respectively, 85 (versus MET+SUL) and 137 (versus MET+INS).
Cost results In a hypothetical cohort of 1,000 overweight patients, the discounted additional costs with ROS+MET were EUR 2.0 million in comparison with MET+SUL and EUR 1.6 million in comparison with MET+INS.
In a hypothetical cohort of 1,000 obese patients, the discounted additional costs with ROS+MET were EUR 2.0 million in comparison with MET+SUL and EUR 1.5 million in comparison with MET+INS.
Synthesis of costs and benefits Incremental cost-effectiveness and cost-utility ratios were calculated to combine the costs and benefits.
In the cohort of overweight patients, the incremental cost per LY gained with ROS+MET was EUR 23,755 in comparison with MET+SUL and EUR 25,205 in comparison with MET+INS.
The incremental cost per QALY gained with ROS+MET was EUR 16,414 in comparison with MET+SUL and EUR 9,406 in comparison with MET+INS.
In the cohort of obese patients, the incremental cost per LY gained with ROS+MET was EUR 27,225 in comparison with MET+SUL and EUR 29,860 in comparison with MET+INS.
The incremental cost per QALY gained with ROS+MET was EUR 23,514 in comparison with MET+SUL and EUR 11,174 in comparison with MET+INS.
The sensitivity analysis showed that none of the changes in model inputs led to a cost per QALY higher than the threshold of EUR 30,000, which is commonly used in Spain.
Authors' conclusions Rosiglitazone (ROS) in combination with metformin (MET) was a cost-effective treatment for both obese and overweight patients who failed MET monotherapy in Spain.
CRD COMMENTARY - Selection of comparators The rationale for the selection of the comparators was clear since the new treatment (including ROS) was compared with conventional care, as recommended in Spain. Dosages were also reported. You should decide whether they are valid comparators in your own setting.
Validity of estimate of measure of effectiveness The effectiveness evidence was derived from published sources. However, it was not stated whether a systematic review of the literature was undertaken and the primary studies appear to have been identified selectively. In general, few details of the primary studies were provided and it was therefore difficult to assess the validity of the primary sources. Further, the issue of the homogeneity of the studies was not addressed and sensitivity analyses were not performed on the clinical data. Several country-specific data were used.
Validity of estimate of measure of benefit QALYs and LYs are the most appropriate benefit measures because they capture the impact of the intervention on quality of care and survival, which are the most relevant dimensions of health for patients with Type 2 diabetes. Utility was derived from the literature and the instrument used to assess the utility weights was reported. The use of QALYs permits comparisons with the benefits of other health care interventions. Discounting was applied, as recommended in economic evaluation guidelines, and the impact of alternative discount rates was investigated.
Validity of estimate of costs The costs included were consistent with the perspective adopted in the study. A detailed breakdown of the cost items was provided and unit costs were presented for most items. However, limited information on resource consumption was given, which limits the possibility of replicating the cost analysis in other settings. The cost estimates were specific to the study setting and few sensitivity analyses were carried out. The source of the data was given for all costs. The price year was reported, which will facilitate reflation exercises in other time periods. The authors stated that the decision model reflected the true costs of care in Spain.
Other issues The authors did not compare their findings with those from other studies. They also did not address the issue of the generalisability of the study results to other settings. Few sensitivity analyses were carried out and the study focused on the Spanish setting. In general, the issue of uncertainty and variability around the model parameters was not fully addressed, given that only one-way sensitivity analyses were performed. The analysis referred to obese and overweight patients with Type 2 diabetes and this was reflected in the authors' conclusions. The authors also noted that the limitations of the DiDACT had been published.
Implications of the study The study results support the use of ROS in combination with MET for the treatment of obese and overweight patients with Type 2 diabetes after the failure of MET monotherapy.
Source of funding Supported by GlaxoSmithKline.
Bibliographic details Shearer A T, Bagust A, Ampudia-Blasco F J, Alvarez B M, Escolano E P, Paris G. Lifetime health consequences and cost-effectiveness of rosiglitazone in combination with metformin for the treatment of type 2 diabetes in Spain. PharmacoEconomics 2006; 24(Supplement 1): 49-59 Other publications of related interest Bagust A, Hopkinson PK, Maier W, et al. An economic model of the long-term health care burden of type 2 diabetes. Diabetologia 2001;44:2140-55.
Beale S, Bagust A, Shearer AT, et al. Cost-effectiveness of rosiglitazone oral combination for the treatment of type 2 diabetes in UK. Pharmacoeconomics 2006;24 Suppl 1:21-34.
Shearer AT, Bagust A, Liebl A, et al. Cost-effectiveness of rosiglitazone oral combination for the treatment of type 2 diabetes in Germany. Pharmacoeconomics 2006;24 Suppl 1:35-48.
Indexing Status Subject indexing assigned by NLM MeSH Adult; Cost-Benefit Analysis; Diabetes Complications /economics; Diabetes Mellitus, Type 2 /drug therapy /economics; Drug Therapy, Combination; Economics, Pharmaceutical; Female; Hospitalization /economics; Humans; Hypoglycemic Agents /economics /therapeutic use; Insulin /therapeutic use; Male; Metformin /therapeutic use; Middle Aged; Obesity /complications /economics; Quality-Adjusted Life Years; Spain; Thiazolidinediones /economics /therapeutic use AccessionNumber 22006008100 Date bibliographic record published 31/08/2006 Date abstract record published 31/08/2006 |
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