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Cost implications of selective preoperative risk screening in the care of candidates for peripheral-vascular operations |
Shaw L J, Hachamovitch R, Cohen M, Berman D S, Borges-Neto S, Udelson J E, Heller G V, Eisenstein E L, Eagle K A, Hendel R C, Miller D D |
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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 Preoperative screening of patients undergoing peripheral vascular operations.
Economic study type Cost-effectiveness analysis.
Study population Patients at intermediate risk for coronary disease.
Setting Hospital. The study was carried out in the USA.
Dates to which data relate Effectiveness data were collected from studies previously published between 1980 and 1995. Resource use data were collected from studies previously published between 1990 and 1996. The price year was 1994.
Source of effectiveness data Effectiveness data were derived from a review of previously published studies.
Modelling A decision analytic model and Monte Carlo simulation was used to measure the costs and outcomes of each screening strategy.
Outcomes assessed in the review The outcomes assessed in the review included age of patients, frequency of typical angina, of congestive heart failure, of diabetes and history of myocardial infarction.
Study designs and other criteria for inclusion in the review Only articles published in English in a peer-reviewed journal were considered. Only studies with broad generalisability and those with a narrower spectrum of generalisability, but with few methodologic flaws were included. Only patient cohorts whose rates of coronary disease or related symptoms ranged from 30% to 60% were included. Studies on major general non-vascular operations were excluded.
Sources searched to identify primary studies The MEDLINE database was searched.
Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Investigators conducting quality assessment were blinded to author and institutional data, and the assessment was performed during two independent sessions.
Number of primary studies included Approximately 32 studies were included in the review.
Methods of combining primary studies Probability values were a weighted average of all raw probability values. Values were weighted according to the study sample size. Probability values (95% confidence intervals) were derived with an empirical Bayes random effects model.
Investigation of differences between primary studies Results of the review Compared with patients who underwent cardiac catheterisation, patients who underwent dipyridamole stress perfusion imaging were older with a greater frequency of prior myocardial infarction and diabetes. Patients who underwent dobutamine stress echocardiography were similar to the other two patient cohorts with respect to age and history of myocardial infarction.
Measure of benefits used in the economic analysis The number of life years saved was used as the main benefits measure. Apart from this measure, the rate of cardiac death or myocardial infarction, the rate of cancellation of operations, the rate of performance of coronary revascularisation, and evidence of ischemia or disease were also considered.
Direct costs Costs were discounted at 5%. Quantities and costs were not reported separately. Direct costs included the cost of vascular operation, the cost of procedures such as catheterisation, the cost of peri-operative and post-operative complications. The quantity/cost boundary adopted was that of the hospital. The estimation of quantities and costs was based on actual data. Cost estimates were based on direct cost estimates from the Duke University microcost accounting system and Medicare hospital charges. The cost of complications was based on published data. The price year was 1994.
Statistical analysis of costs Total costs were compared by means of analysis of variance.
Sensitivity analysis Sensitivity analysis was conducted on surgical costs, in-hospital complication rates, and rates of coronary disease for the population.
Estimated benefits used in the economic analysis The rate of cancellation of operations was 6.4% under pharmacologic stress imaging and 12% under catheterisation, (p=0.017). The rate of performance of pre-operative coronary revascularisation was 9% under pharmacologic stress imaging and 16% under catheterisation, (p=0.001). The rate of cardiac death or myocardial infarction was 1% of patients with normal intravenous dipyridamole myocardial perfusion scans, 7% of patients with fixed subtypes, and 9% of patients with reversible subtypes, (p=0.0001). Among patients with dobutamine-induced echocardiographic dissynergy, 23.1% had a peri-operative ischaemic event compared with 0.4% of patients with a normal stress echocardiogram, (p<0.0001). No pre-operative coronary revascularisation was conducted in 18.1% of patients under pharmacologic stress imaging and in 10.2% of patients under catheterisation, (p=0.002). No evidence of ischemia or disease was found in 6.9% of patients under pharmacologic stress imaging and in 3.2% of patients under catheterisation, (p=0.02). Among patients with a history of coronary artery disease, the cardiac event rate was 5% among patients with a normal or fixed defect and 19% among patients with a redistribution abnormality, (p=0.0001).
Cost results Total costs amounted to $33,162 for pharmacologic stress imaging and to $42,280 for catheterisation, (p=0.001). Total costs of the 'do nothing' strategy amounted to $23,351; significantly lower than the costs of the two other strategies, (p=0.01).
Synthesis of costs and benefits The cost-effectiveness of non-invasive screening was $33,338 per life year saved for a 60-year-old patient, $26,890 per life year saved for a 70-year-old patient and $21,790 per life year saved for an 80-year-old patient. The cost-effectiveness of coronary revascularisation among patients with abnormal results of non-invasive tests was $59,861 per life year saved for a 60-year-old patient, $48,293 per life year saved for a 70-year-old patient, and $39,142 per life year saved for an 80-year-old patient.
Authors' conclusions Substantial cost savings were predicted when selective non-invasive stress imaging was added to pre-operative screening for patients about to undergo vascular operations. With a selective screening approach, the economic impact of initial diagnostic testing may be minimised without compromising patient outcomes.
CRD COMMENTARY - Selection of comparators The rationale for the choice of the comparators was clear. Validity of estimate of measure of benefit The relevant measures of benefit were examined. The results were based on a systematic review of the literature (published and other). Identified studies suffered from small sample size, short follow-up times, differences in referral cohorts, temporal shifts in pre-discharge medical care. The problems of referral bias and publication bias in the literature reviewed also need to be addressed. Validity of estimate of costs Only direct costs were included. Cost estimates were derived from a variety of sources. The relevance of these cost estimates to a particular setting or country was unclear. Other issues The generalisability of effectiveness and cost results was not discussed. The authors list the specific limitations of their study in conjunction with the well accepted problems of decision analysis/heterogeneity of data generating input parameters. Implications of the study Using the reported selective screening approach, substantial cost savings may be anticipated for patients undergoing vascular operations. The cost-effectiveness of preoperative screening is enhanced among patients older than 70 years.
Bibliographic details Shaw L J, Hachamovitch R, Cohen M, Berman D S, Borges-Neto S, Udelson J E, Heller G V, Eisenstein E L, Eagle K A, Hendel R C, Miller D D. Cost implications of selective preoperative risk screening in the care of candidates for peripheral-vascular operations. American Journal of Managed Care 1997; 3(12): 1817-1827 Other publications of related interest Shaw L J, Eagle K A, Gersh B J, Miller D D. Meta-analysis of intravenous dipyridamole thallium-201 imaging (1985-1994) and dobutamine echocardiography (1990-1994) for risk stratification prior to vascular surgery. Journal of the American College of Cardiology 1996;27:787-798.
Indexing Status Subject indexing assigned by NLM MeSH Decision Trees; Diagnostic Tests, Routine /economics; Hospital Costs; Hospitals, University; Humans; North Carolina /epidemiology; Outcome Assessment (Health Care); Patient Selection; Postoperative Complications /epidemiology; Preoperative Care; Risk Assessment; United States; Value of Life; Vascular Diseases /economics /surgery AccessionNumber 21998000521 Date bibliographic record published 30/11/1999 Date abstract record published 30/11/1999 |
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