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Cost-consequence analysis in a French setting of screening and optimal treatment of nephropathy in hypertensive patients with type 2 diabetes |
Palmer A J, Chen R, Valentine W J, Roze S, Bregman B, Mehin N, Gabriel S |
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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 authors assessed nephropathy screening and the subsequent treatment of individuals found to be positive and compared this with no screening. Screening was performed annually using Micral II semi-quantitative urine dipstick test strips. Treatment was the addition of irbesartan 300 mg/day to the patient's conventional therapy.
Study population The hypothetical study population comprised hypertensive patients with Type 2 diabetes with nephropathy.
Setting The setting was primary care. The economic study was carried out in France.
Dates to which data relate The effectiveness data related to studies published between 2000 and 2004. The costs were reported in 2002 prices.
Source of effectiveness data The authors used a review to inform transition probabilities between the identified health states used in their model. For instance, the probability of progression from no nephropathy to microalbuminuria, from microalbuminuria to early overt nephropathy, from early overt nephropathy to advanced overt nephropathy, and from advanced overt nephropathy to DSC or end-stage renal disease (ESRD). The impact of treatment on progression probabilities was also estimated from the review. The authors reported that the probabilities used had been reported elsewhere (Palmer et al. 2002, see 'Other Publications of Related Interest' below for bibliographic details). Mortality data, specifically the relative risk of death in each of the defined health states, were also obtained from the review, as were the sensitivity and specificity of the screening test.
Modelling The authors used a Markov/Monte Carlo model that simulated eight disease states to indicate the progression of renal disease in the study population. Progression was from no nephropathy to microalbuminuria, early overt nephropathy, advanced overt nephropathy, doubling of serum creatinine (DSC), transplant and death. Additional states modelled the impact of screening, correct and incorrect diagnosis, and treatment. The transition probabilities were informed by a review of the literature. The model was developed using TreeAge Pro software (TreeAge Software Inc., Williamstown, MA). A lifetime horizon was adopted (25 years). At baseline, patients were simulated throughout the model according to prevalence data gathered during the review.
Sources searched to identify primary studies The data were principally taken from a number of published studies relating to clinical trials (the BENEDICT, EDICT, IRMA-2 and IDNT trials). The authors described the relative merits of these studies in being applicable to the study population. French ESRD therapeutic and outcomes data were used where possible. The author accurately reported the sources of their data inputs.
Methods used to judge relevance and validity, and for extracting data The authors did not report details of how they searched for relevant data. However, they appear to have selected references that matched the requirements of their model.
Measure of benefits used in the economic analysis The summary measures of health benefit were the life expectancy and quality-adjusted life-years (QALYs). Health state utilities were assigned to each health state identified in the Markov model and multiplied by the length of time spent in that state. The utility data were taken from two published sources (Brown et al. 2000 and Tengs et al. 2000, see 'Other Publications of Related Interest' below for bibliographic details). The benefits were discounted at a rate of 3%.
Direct costs The costing analysis was carried out from the perspective of a French third-party health insurance payer. The analysis included the costs of screening (general practitioner consultation, and test strips) and differentiated between positive and negative test results and their consequences. French-specific costs of ESRD were incorporated (dialysis and transplantation). These estimates included elements of hospital day costs, medical costs for dialysis, erythropoietin, dietician consultations, laboratory tests, blood pressure monitoring and blood transfusions. The costs were reported in 2002 prices and were discounted at 3% to adjust for time preference over the duration of the model. There was no report that any costs were reflated. The source of the cost estimates was not reported.
Statistical analysis of costs The costs were treated as deterministic, although distributions were estimated for the purpose of simulation.
Indirect Costs Productivity costs were not relevant to the perspective adopted.
Sensitivity analysis A second-order Monte Carlo simulation was used to account for multiple parameter uncertainty in the transition probabilities, patients' ages, prevalence of microalbuminuria and overt nephropathy, and sensitivity and specificity of screening. A sensitivity analysis was used to explore the implications of varying the baseline age of the patients, and the assumption that 85% of patients with overt nephropathy at baseline would have early overt nephropathy and 15% would have advanced overt nephropathy. The discount rates and time horizon were also subject to sensitivity analysis.
Estimated benefits used in the economic analysis Non-discounted life expectancy was 11.50 (+/-6.64) years without screening and 11.87 (+/- 7.17) years with screening and optimal treatment. The difference was 0.38 (+/- 0.59) years.
Discounted life expectancy improved by 0.2 (+/- 0.24) years.
QALYs (discounted) were 8.58 (+/- 3.73) without screening and 8.87 (+/- 4.02) with screening and optimal treatments. The difference was 0.29 (+/- 0.32) QALYs.
Cost results The total 25-year costs per patient (discounted) were EUR 17,968 (+/- 21,047) without screening and EUR 13,155 (+/- 13,283) with screening. The difference was EUR 4,812 (+/- 7,882).
The authors noted that a cost-saving occurred after 8 years.
Synthesis of costs and benefits The sensitivity analysis revealed that a short time horizon still led to improvements in patients' outcomes as well as cost-savings, and that the discount rate and proportion of patients with overt early nephropathy had little impact on the relative outcomes. Screening had the most benefit in younger patients.
Authors' conclusions The authors concluded that annual screening in their patient population "may lead to substantial improvements in long-term patient outcomes, with the added benefit of overall cost savings".
CRD COMMENTARY - Selection of comparators The authors aimed to assess the cost-effectiveness of screening and, to this end, appropriately used screening and no screening as their comparators. Although these comparators are applicable to any setting, readers may wish to consider whether the specific method and timing of screening are applicable to their own setting before making any generalisations of the results.
Validity of estimate of measure of effectiveness Although the sources used to provide data for the model were clear, the methods used to ascertain these data were not well reported. It was unclear whether a systematic review of the literature was carried out and, therefore, whether data used in the model were representative of the population of interest, and indeed wider populations, or whether less accurate and potentially biased data informed the model. However, the authors reported that details had been published elsewhere and readers were referred to these other sources for more information. The authors noted that French sources were used where possible in order to increase the specificity of the model. Validity of estimate of measure of benefit Life expectancy and QALYs were used as the summary measures of health benefit, despite the authors suggesting that they had carried out a cost-consequences analysis (which implies no summary estimate of health benefit). These measures are widely comparable with other analyses of health-related technologies, thus allowing readers to understand the broader cost-effectiveness of these technologies. Further information on the sources of utilities might have reassured the reader of the applicability of these data to the population of interest. Nevertheless, the authors provided full bibliographic details, thus enabling the interested reader to find out more.
Validity of estimate of costs The costing was carried out from the perspective of a third-party payer. Costs relevant to this perspective were included, although the sources of them could have been reported in more detail. For instance, were such costs obtained directly for a third-party payer or were health care provider charges used as the basis for unit costs? Given the proximity of the total cost estimates and the wide ranges associated with the estimates, small changes in cost due to inaccuracies or even a change in the perspective of the model might induce changes in the results, and hence in the principle conclusions of the analysis. The costs were appropriately discounted and a price year was reported. The analysis would have been improved by the inclusion of a detailed breakdown of the total cost element into component parts.
Other issues The authors compared their findings with other studies and reported that the results supported existing evidence. The authors used French-specific data to ensure the specificity of their model to the patient population therefore, whilst generalisable within French settings, authors from a wider region should compare the data inputs with those applicable to their own setting before generalising the results. The results were clearly presented and easy to interpret and the conclusions accurately reflected the results reported. The authors provided a useful discussion of how the analysis focused on a conservative estimate of cost-effectiveness and the true cost-effectiveness may therefore be better than reported. The authors reported the restricted study population as both a strength and potential limitation to the study; the study is not able to draw conclusions about all patients with Type 2 diabetes and hypertension.
Implications of the study The authors did not make any recommendations for policy or practice following on from their study, although they did note that "financial concerns should not be a barrier to implementation of improved screening programs in this patient group". Further work might explore the cost-effectiveness implications to all patients with Type 2 diabetes and hypertension.
Source of funding Funded by Sanofi-Aventis and Bristol-Myers Squibb.
Bibliographic details Palmer A J, Chen R, Valentine W J, Roze S, Bregman B, Mehin N, Gabriel S. Cost-consequence analysis in a French setting of screening and optimal treatment of nephropathy in hypertensive patients with type 2 diabetes. Diabetes and Metabolism 2006; 32(1): 69-76 Other publications of related interest Because readers are likely to encounter and assess individual publications, NHS EED abstracts reflect the original publication as it is written, as a stand-alone paper. Where NHS EED abstractors are able to identify positively that a publication is significantly linked to or informed by other publications, these will be referenced in the text of the abstract and their bibliographic details recorded here for information.
Palmer AJ, Annemans L, Roze S, et al. An economic evaluation of irbesartan in the treatment of patients with type 2 diabetes, hypertension and nephropathy Trial (IDNT) in the Belgian, and French settings. Nephrol Dial Transplant 2003;18:2059-66.
Brown GC, Brown MM, Sharma S, et al. Quality of life associated with diabetes mellitus in an adult population. J Diabetes Complications 2000;14:18-24.
Tengs TO, Wallace A. One thousand health-related quality-of-life estimates. Med Care 2000;38:583-637.
Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Aged, 80 and over; Computer Simulation; Cost of Illness; Diabetes Mellitus, Type 2 /economics /mortality /therapy; Diabetic Angiopathies /economics /mortality /therapy; Diabetic Nephropathies /economics /mortality /therapy; France; Humans; Hypertension /economics /mortality /therapy; Incidence; Kidney Failure, Chronic /economics /epidemiology /therapy; Markov Chains; Middle Aged; Monte Carlo Method; Probability AccessionNumber 22006001309 Date bibliographic record published 31/08/2007 Date abstract record published 31/08/2007 |
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