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Cost-minimization and the number needed to treat in uncomplicated hypertension |
Pearce K A, Furberg C D, Psaty B M, Kirk J |
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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 First-line antihypertensive drugs for treatment of uncomplicated mild to moderate hypertension.
Economic study type Cost-effectiveness analysis.
Study population Hypothetical patients with uncomplicated mild to moderate hypertension. Two distinct patient groups were investigated:middle aged patients (aged 21 to 64) and the elderly (aged between 60 and 97).
Setting Primary care setting. The economic study was carried out in North Carolina, USA.
Dates to which data relate The main effectiveness data were taken from studies published during the period 1970-1992. The drugs costs were taken from a drug handbook published in 1996; the drug resources were estimated using expert opinion but were verified against drug handbooks published in 1995 and 1996. The price year was 1996.
Source of effectiveness data The effectiveness data were derived from previously published sources and expert opinion.
Outcomes assessed in the review The review assessed the number of clinical events, namely stroke, myocardial infarction and death, occurring within the study period.
Study designs and other criteria for inclusion in the review Randomised clinical trials comparing drug treatments for uncomplicated mild to moderate hypertension in either the middle aged or elderly were included in the review. Only studies published in English were considered and were from the period 1970-1992.
Sources searched to identify primary studies MEDLINE was searched to identify primary studies, and studies were also identified through previous overviews and reviews of the references of identified papers.
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 Seven studies were identified for the middle aged group and eight for the elderly group.
Methods of combining primary studies Primary studies were combined according to the principles of meta-analysis although no precise details were given.
Investigation of differences between primary studies Results of the review The risk ratios were: for fatal or nonfatal coronary heart disease, 0.91 (middle age), 0.82 (elderly); fatal or nonfatal stroke, 0.56 (middle age), 0.65 (elderly); death from any cause, 0.87 (middle age), 0.89 (elderly); and nonfatal event or death, 0.82 (middle age), 0.84 (elderly).
Methods used to derive estimates of effectiveness Estimates of effectiveness were also based on the authors' assumptions.
Estimates of effectiveness and key assumptions The authors made the assumption that all of the drugs investigated were equally effective at reducing stroke, myocardial infarction and death as observed in the trials for diuretics and beta-blockers included within the review.
Measure of benefits used in the economic analysis Since the authors assumed that there was no difference in effectiveness between the drugs, the economic analysis was based on the difference in costs only (cost-minimization).
Direct costs The basic analysis included only the costs of the drugs used in treatment, based upon the assumption that non-drug direct costs were equivalent for all the drug classes. The resource use was based upon the number of patients needed to be treated over five years to prevent one clinical event, determined via the risk ratios identified within the review, and estimates of drug doses equivalent in respect of blood pressure reduction, determined by five clinical experts. The prices used were average wholesale price derived from a published source - the average for all generic formulations was used, where applicable, otherwise brand name drugs were used. The analysis was undertaken using the most commonly prescribed drug in each class and also for the least expensive drug in each class. The costs were not discounted and were assumed to remain stable over the five year period of interest. The price year was 1996.
Additional analyses were also undertaken: firstly incorporating the costs of physician visits and laboratory tests within the analysis and secondly incorporating potassium chloride supplementation within the cost of diuretic treatment. Within the first additional analysis, the number and the price of physician visits and laboratory tests were reported separately, with the prices based upon fee schedules although no details were given regarding the source of the estimate of the number of visits and tests required. Within the second additional analysis, the dose and price of the supplementary drugs were reported separately with the prices the average wholesale price of the generic drug as given in a published source. No details were given concerning the source of the drug dose. The percentage of people requiring the supplementary drug was assumed to be 25% for each of two drugs.
Statistical analysis of costs Sensitivity analysis A sensitivity analysis was carried out to examine the impact upon the results of altering the key assumptions of the study: equal drug effectiveness; equal non-drug direct outpatient costs and equipotent drug doses, through one-way sensitivity analysis.
Estimated benefits used in the economic analysis Cost results The costs were reported in terms of the expenditure on drugs required to prevent one myocardial infarction, stroke or death among patients with mild to moderate uncomplicated hypertension. The costs for middle aged patients using the most common treatment in each class were $4,730 (diuretic); $ 105,092 (beta-blocker); $156,520 (ACE inhibitor); $194,360 (alpha-blocker); and $346,236 (calcium blocker). Using the least expensive treatment in each class the costs for middle aged patients were $4,730 (diuretic); $54,782 (beta-blocker); $94,170 (ACE inhibitor); $151,188 (alpha-blocker); and $128,570 (calcium blocker). For elderly patients using the most common treatment in each class the costs were $1,595 (diuretic); $35,438 (beta-blocker); $52,780 (ACE inhibitor); $65,540 (alpha-blocker); and $116,754 (calcium blocker). Using the least expensive treatment in each class the costs were $1,595 (diuretic); $18,473 (beta-blocker); $31,755 (ACE inhibitor); $50,982 (alpha-blocker); and $43,355 (calcium blocker).
Synthesis of costs and benefits Authors' conclusions The prevention of cardiovascular events in patients with mild to moderate uncomplicated hypertension can be achieved at a lower cost through the use of generic diuretics and beta-blockers and these treatments should form the basis of therapy in these patients.
CRD COMMENTARY - Selection of comparators The reason for the choice of treatments investigated is clear: each is commonly used within the treatment of uncomplicated mild to moderate hypertension. You, as a user of this database, should consider if these health technologies apply to your setting.
Validity of estimate of measure of benefit The authors made the assumption that the different drug classes were equally effective at reducing cardiovascular events, within the patient groups. This enabled the authors to concentrate the analysis upon the costs of each class of drugs. This assumption was tested within the sensitivity analysis. The effectiveness measure used for the drugs was determined through an extensive search of the literature and there is no evidence of selective use of data.
Validity of estimate of costs Resource quantities were reported separately from prices. Prices were derived from published drug schedules in the USA, which whilst internally valid are not generalisable to the UK. The analysis focused upon the costs of drugs and omitted any other aspects of treatment and costs to others in society, for example, physician visits, side effects, drug interactions, supplementary drugs required and patient costs. Some of these issues were dealt with in additional analyses and others were considered qualitatively in the discussion.
Other issues The authors relied on published data from the literature, which has inherent biases. The data are often from specialised medical settings and are not externally valid. The authors discussed the limitations of generalising the study results to other settings and patient groups. Other studies were mentioned but there was no formal comparison of results.
Implications of the study Further studies are required to determine the effectiveness of the newer drug classes.
Bibliographic details Pearce K A, Furberg C D, Psaty B M, Kirk J. Cost-minimization and the number needed to treat in uncomplicated hypertension. American Journal of Hypertension 1998; 11(5): 618-629 Indexing Status Subject indexing assigned by NLM MeSH Antihypertensive Agents /economics; Cerebrovascular Disorders /prevention & Cost Control; Drug Costs; Humans; Hypertension /drug therapy; Myocardial Infarction /prevention & Sensitivity and Specificity; control; control AccessionNumber 21998000866 Date bibliographic record published 30/06/1999 Date abstract record published 30/06/1999 |
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