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Are the WOSCOPS clinical and economic findings generalizable to other populations? A case study for Belgium |
Caro J J, Huybrechts K F, De Backer G, De Bacquer D, Closon M C |
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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 Primary prevention of coronary heart disease with pravastatin.
Economic study type Cost-effectiveness analysis.
Study population The study investigated middle-aged men with hypercholesterolaemia and with no history of myocardial infarction.
Setting The setting was hospital. The economic study was carried out in Belgium.
Dates to which data relate Effectiveness and resource use data were collected from studies published between 1984 and 1996 and from two databases (1980-1984, 1981-1994). Cost data were taken from a 1995 hospital database. The price year was 1998.
Source of effectiveness data The effectiveness data were derived from a review of the literature.
Modelling A five-year Markov decision analytic model was used to determine the cost-effectiveness of pravastatin. An exponential regression model of the reference risk on a number of risk factors was also used.
Outcomes assessed in the review The review assessed the population's reference risk, and the relative risk reduction due to treatment.
Study designs and other criteria for inclusion in the review Effectiveness estimates were derived from the West of Scotland Coronary Prevention Study (WOSCOPS) clinical trials and Belgian epidemiological data.
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 Summary statistics of individual studies were used.
Number of primary studies included At least three primary studies were included in the review.
Methods of combining primary studies The narrative method was used.
Investigation of differences between primary studies Results of the review The reference risk in the placebo group was 15.8% over five years. Use of pravastatin reduced this risk by 22%, resulting in a 3.48% absolute risk reduction.
Measure of benefits used in the economic analysis Life years gained were used as the measure of benefits. Benefits were discounted at an annual rate of 5%.
Direct costs Direct costs were discounted at an annual rate of 5%. Quantities and costs were reported separately. Direct costs included costs of initial management, costs related to length of stay and stay in the intensive care unit, and drug costs. The quantity/cost boundary adopted was that of a health insurance agency. The estimation of quantities and costs was based on actual data. Costs were taken from a hospital database. Values were inflated to 1998 using the Belgian Medical Inflation Index.
Statistical analysis of costs No statistical analysis was reported.
Indirect Costs Indirect costs were not included.
Sensitivity analysis The results of a Monte Carlo multivariate sensitivity analysis were reported.
Estimated benefits used in the economic analysis The mean risk of cardiovascular disease was 14.5% over five years.
The absolute risk reduction was 3.19% (3.48% in WOSCOPS).
The five year cardiovascular risk, excluding patients with one or more possible signs of overt disease, was 13.5% (13.7% in WOSCOPS).
The use of pravastatin in asymptomatic men would prevent 297 out of 10,000 from developing overt cardiovascular disease over five years, thereby saving 3,104 life years and 1,435 hospital bed days.
Of the 297 men, 30 would have died immediately from cardiovascular disease, 129 would have suffered a first non-fatal myocardial infarction, 63 would have undergone hospitalisation for angina, 31 would have needed revascularisation, and 44 would have experienced a non-fatal stroke or TIA.
Cost results Preventing these events in 10,000 men would cost EU 38.7 million.
Synthesis of costs and benefits The cost-effectiveness ratio was EU 12,500 per life year gained using undiscounted benefits and EU 29,900 per life year gained using discounted benefits. These results held over a wide range of input values.
Authors' conclusions The clinical and economic findings from WOSCOPS can be generalised to other populations.
CRD COMMENTARY - Selection of comparators A justification was given for the comparators used, namely no primary prevention. You, as a user of the database, should decide if these health technologies are relevant to your setting.
Validity of estimate of measure of effectiveness The authors utilised, as their primary source of effectiveness data, a good quality trial (WOSCOPS) and modelled effectiveness using epidemiological and demographic data for a Belgian population, which was an appropriate approach to test the generalisability hypothesis. In conjunction with the sensitivity analysis the results are likely to have high validity.
Validity of estimate of measure of benefit The estimation of benefits was appropriately obtained directly from the effectiveness analysis.
Validity of estimate of costs Good features of the cost analysis were that all relevant direct cost categories were included; quantities and costs were reported separately; and the price year was reported. However, charges were used to proxy prices; cost estimates did not include the portion paid by patients; and neither management costs subsequent to the first admission to hospital nor pre-admission costs were considered. The validity of the cost results was enhanced by appropriate sensitivity analyses over plausible ranges.
Other issues The authors did make appropriate comparisons of their findings with those from other studies and the issue of generalisability to other settings was addressed. The authors did not present their results selectively. The study considered middle-aged men with hypercholesterolaemia and with no history of myocardial infarction in a Belgian setting, and this was reflected in the authors' conclusions. The authors appear to have been successful in considering the generalisability of results in the source setting for Belgium. This type of study is key in terms of the methodology of health economics and concerns regarding the validity of clinical effectiveness findings in reasonably similar populations, using local cost information.
Implications of the study Primary prevention with pravastatin in Belgium represents good value for money. The findings from WOSCOPS are generalisable to other populations with similar characteristics in terms of gender, age, and cholesterol level. Extrapolation of the results to other HMG-CoA reductase inhibitors is not permitted.
Source of funding Supported in part by a grant from Bristol-Myers Squibb, Belgium.
Bibliographic details Caro J J, Huybrechts K F, De Backer G, De Bacquer D, Closon M C. Are the WOSCOPS clinical and economic findings generalizable to other populations? A case study for Belgium. Acta Cardiologica 2000; 55(4): 239-246 Other publications of related interest Shepherd J, Cobbe S M, Ford I, Isles C G, Lorimer A R, Macfarlane P W, McKillop J H, Packard C J, for the West of Scotland Coronary Prevention Study Group. Prevention of coronary heart disease with pravastatin in men with hypercholesterolaemia. New England Journal of Medicine 1995;333:1301-7.
Caro J, Klittich W, McGuire A, Ford I, Norrie J, Pettitt D, McMurray J, Shepherd J, for the West of Scotland Coronary Prevention Study Group. West of Scotland Coronary Prevention Study: weighing the costs and benefits of primary prevention with pravastatin. BMJ 1997;7122:1577-82.
Indexing Status Subject indexing assigned by NLM MeSH Anticholesteremic Agents /economics /therapeutic use; Belgium; Coronary Disease /economics /prevention & Cost-Benefit Analysis; Humans; Male; Middle Aged; Monte Carlo Method; Multivariate Analysis; Pravastatin /economics /therapeutic use; Primary Prevention; Randomized Controlled Trials as Topic; Risk; Risk Factors; Scotland; control AccessionNumber 22000001711 Date bibliographic record published 31/08/2001 Date abstract record published 31/08/2001 |
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