|Health economic implications of irbesartan treatment versus standard blood pressure control in patients with type 2 diabetes, hypertension and renal disease: a Hungarian analysis
|Palmer A J, Valentine W J, Ray J A, Roze S, Muszbek N
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.
The study evaluated the clinical and economic impact of irbesartan added to usual care, compared with standard antihypertensive medications, in patients with Type 2 diabetes, hypertension and microalbuminuria in the Hungarian context. It was concluded that irbesartan led to lower costs and higher effectiveness in comparison with usual care. Overall, the study was based on a sound methodology and on good reporting, although the cost side of the analysis was not very comprehensive in terms of the description of the categories of costs.
Type of economic evaluation
The objective of the study was to evaluate the clinical and economic impact of irbesartan added to usual care, compared with standard antihypertensive medications, in patients with Type 2 diabetes, hypertension and microalbuminuria.
Two interventions were considered: standard antihypertensive medications (i.e. diuretics, beta-blockers, alpha-or beta-blockers, etc., excluding angiotensin-converting enzyme inhibitors) versus irbesartan 300 mg/day plus standard antihypertensive medications.
A published Markov model on the progression of disease for patients with Type 2 diabetes, hypertension and microalbuminuria was adapted to the Hungarian setting in order to determine the long-term impact of irbesartan treatment, based on the key results from two clinical trials. A lifetime horizon was adopted. The authors stated that the perspective of the third-party Hungarian health insurance payer was adopted.
The clinical data used in the model were derived from a selection of known relevant studies. The authors selected the most appropriate estimates from the available evidence found in the literature. The treatment effect was taken from a pivotal trial for irbesartan (the Irbesartan in Reduction of Microalbuminuria-2 study). Transition probabilities used to populate the model were derived from the same study and from a national database, in order to reflect the authors’ context. Mortality rates were mainly taken from Danish studies. The key clinical inputs were transition rates of the progressive disease, with and without irbesartan.
Monetary benefit and utility valuations:
Measure of benefit:
The primary benefit measure was life expectancy, which was estimated using the decision model. An annual discount rate of 5% was applied. Years free of end-stage renal disease (ESRD) and the incidence of ESRD were also reported.
The analysis focused on the estimation of the incremental costs of adding irbesartan to usual therapy, and included the costs of irbesartan and treatment of ESRD (dialysis or transplant). The costs were derived from total third-party reimbursement rates. A breakdown of cost items was not given. The costs were in Hungarian forints (HUF). The price year was 2002. The costs were discounted at an annual rate of 5%.
Analysis of uncertainty:
A second-order Monte Carlo simulation was used to determine the mean, median and confidence intervals of clinical and economic outcomes. Multiple univariate sensitivity analyses were also carried out by varying cost estimates and annual death rates. A further analysis considered the different levels of urinary albumin excretion (UAE) at which patients entered the state of advanced overt nephropathy.
The discounted life-years were 7.62 with usual care and 8.16 with irbesartan (difference 0.54).
The 25-year costs were HUF 1,770,197 with usual care and HUF 1,250,204 with irbesartan (difference HUF 519,993 in favour of irbesartan). Irbesartan became cost-saving over usual care after approximately 13 years of therapy.
The costs and benefits were not combined in a cost-effectiveness ratio as irbesartan was the dominant strategy (both more effective and less expensive).
The sensitivity analysis corroborated the base-case findings in that none of the variations in model inputs altered the conclusions of the primary analysis.
The authors concluded that irbesartan was a dominant treatment (lower costs and higher effectiveness), compared with usual antihypertensive therapy, in patients with Type 2 diabetes, hypertension and microalbuminuria in Hungary .
The selection of the comparators under examination was appropriate as they were relevant in the authors’ setting, where the new therapy was compared with standard care. The agents used as routine antihypertensive therapy were clearly described.
The clinical data were derived from published studies, which may have been identified selectively as the methods and conduct of any literature review were not reported. The sources used, namely a clinical trial for irbesartan treatment effect and some transition probabilities and a national administrative database to adapt the decision model to the authors context, represented appropriate choices. A description of the process used to determine the clinical estimates and benefit measures was given.
The analysis of the costs was consistent with the authors' stated perspective. Overall, the details of the cost analysis were not transparent as the costs were presented as macro-categories and were not broken down into single items. This may limit the possibility of replicating the analysis in other settings. The sources of the costs were typical national reimbursement rates in the authors’ countries, but may not be applicable to other settings. The price year was reported, which will aid reflation exercises in other time periods.
Analysis and results:
The results of both the base-case and sensitivity analyses were reported clearly. Thus, the analysis was carried out in a transparent fashion, which improves the external validity of the study conclusions. Overall, the issue of uncertainty was satisfactorily addressed, using both deterministic and probabilistic analysis, although the distributions used for the Monte Carlo simulation were not described. The dominance of irbesartan precluded the use of a cost-effectiveness ratio to combine the costs and benefits.
In general, the methodology of the study was well reported and the results of the analysis were clearly described. A weakness of the analysis of the costs was that few details of the cost estimates were given. The conclusions reached by the authors appear appropriate given the objective of the analysis.
Unrestricted grant from Sanofi -Aventis Hungary.
Palmer A J, Valentine W J, Ray J A, Roze S, Muszbek N. Health economic implications of irbesartan treatment versus standard blood pressure control in patients with type 2 diabetes, hypertension and renal disease: a Hungarian analysis. European Journal of Health Economics 2007; 8(2): 161-168
Other publications of related interest
Parving HH, Lehnert H, Brochner-Mortensen J, et al. The effect of irbesartan on the development of diabetic nephropathy in patients with type 2 diabetes. N Engl J Med 2001;345:910-2.
Palmer AJ, Annemans L, Roze S, et al. Cost-effectiveness of early irbesartan treatment versus control (standard antihypertensive medications excluding ACE inhibitors, other angiotensin-2 receptor antagonists, and dihydropyradine calcium channel blockers) or late irbesartan treatment in patients with type 2 diabetes, hypertension and renal disease. Diabetes Care 2004;27:1897-903.
Subject indexing assigned by NLM
Albuminuria /physiopathology; Antihypertensive Agents /administration & Biphenyl Compounds /administration & Cohort Studies; Comorbidity; Costs and Cost Analysis; Diabetes Mellitus, Type 2; Drug Therapy, Combination; Humans; Hungary; Hypertension /drug therapy; Kidney Failure, Chronic /physiopathology; Life Expectancy; Markov Chains; Middle Aged; Outcome Assessment (Health Care); Tetrazoles /administration & dosage /economics /therapeutic use; dosage /economics /therapeutic use; dosage /economics /therapeutic use
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Date abstract record published