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Cost for inpatient care of venous thrombosis: a trial of enoxaparin vs standard heparin |
de Lissovoy G, Yusen R D, Spiro T E, Krupski W C, Champion A H, Sorensen S V |
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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 Use of enoxaparin, a low-molecular weight heparin administered either once or twice per day, in the inpatient care of acute deep venous thrombosis.
Economic study type Cost-effectiveness analysis.
Study population Patients with symptomatic deep vein thrombosis of the proximal or distal lower extremity with or without pulmonary embolism, confirmed by venography or ultra sonography. Exclusion criteria included previous treatment with anticoagulant agents or need for thrombolytic therapy, increased risk of haemorrhage or active haemorrhage, and hypersensitivity to heparin.
Setting Secondary care. The study was conducted at 74 sites in Europe, the United States, Australia and Israel.
Dates to which data relate Effectiveness data were collected between 19 May 1994 and 17 July 1996. Costs relate to 1997.
Source of effectiveness data Effectiveness evidence was derived from a single study.
Link between effectiveness and cost data Costing was undertaken retrospectively on the patients enrolled at participating sites in the United States (339 patients from a total of 900).
Study sample The multinational trial was conducted on 900 patients, randomised to one of the following three treatment groups:
once daily dose of enoxaparin, 298 patients;
twice-daily dose of enoxaparin, 312 patients; and
unfractionated heparin, 290 patients.
The clinical trial included 900 patients, randomly assigned to initial therapy with subcutaneous enoxaparin either once (n = 298), or twice (n = 312) daily, or with dose-adjusted intravenous unfractionated heparin (n = 290). Power calculations related to the sample size were not detailed in this paper.
Study design The study was a partially blinded, randomised, controlled multi-centre, multinational trial. The duration of follow-up was 3 months.
Analysis of effectiveness The analysis was conducted on an intention to treat basis. The main health outcomes used in the analysis were incidence of symptomatic, recurrent deep vein thrombosis and pulmonary embolism. Rates of all-cause hospital re-admissions and of thromboembolism-related re-admissions were also considered. No significant differences in demographic features were observed between the treatment groups, except for a somewhat greater proportion of males in the enoxaparin group (58.7% versus 50%).
Effectiveness results The 3 treatment regimens were equivalent in terms of the incidence of symptomatic, recurrent deep vein thrombosis and pulmonary embolism.
Re-admission rates for all causes were as follows: 20.5% for enoxaparin once daily, 17.1% for enoxaparin twice daily and 26% for unfractionated heparin.
For venous thromboembolism the rates were: 10.7 for enoxaparin once daily, 8.9 for enoxaparin twice daily and 17.3 unfractionated heparin.
Clinical conclusions Use of enoxaparin for deep vein thrombosis is a safe procedure.
Measure of benefits used in the economic analysis The effectiveness analysis showed no difference in effectiveness for the main indicators (incidence of symptomatic, recurrent deep vein thrombosis and pulmonary embolism) for the 3 regimens. As a result, the authors concentrated on the cost analysis, undertaking a cost-minimisation exercise based on a sub-sample of 339 patients (n = 112, 123 and 104 respectively).
Direct costs Direct medical costs were considered in the analysis, which was performed from the perspective of the third-party payer.
The following medical resources were costed.
Professional fees - encounters: primary care initial visit, follow-up visit, specialist visit, nurse visit.
Professional fees - diagnostic procedures: ultrasonography, venography, ventilation/perfusion lung scan, perfusion lung scan, chest x-ray and laboratory tests.
1997 prices were used and costs were not discounted due to the short duration of the study. Quantities (resource use) and costs were presented separately.
Statistical analysis of costs The arithmetic mean and 95% confidence interval (CI) were calculated for the cost of each category of resource and for the total cost for the 3-month episode of care. Means and CIs for the total cost for the episode of care were also compared using a boot-strapping technique that compensates for the non-normal distribution that is typical for the medical expenditure data.
Indirect Costs Indirect costs were not considered.
Sensitivity analysis The authors undertook one-way sensitivity analyses to determine if the findings were robust to variation in the standard unit prices assigned to treatment resources. Values were varied at +/- 50% of the baseline values. Mean cost and 95% CIs were calculated for each low and high unit cost value.
Estimated benefits used in the economic analysis The authors conducted a cost-minimisation analysis; the reader if referred to the effectiveness results reported above.
Cost results Average total cost for the 3-month episode of care was similar across all 3 treatment regimens: once daily dose of enoxaparin $12,166, (95% CI: 10,723 - 13,569); twice-daily dose of enoxaparin $11,558, (95% CI: 10,419 - 12,834); and unfractionated heparin, $12,146, (95% CI: 10,647 - 13,913).
Synthesis of costs and benefits Costs and benefits were not combined, due to the cost-minimisation approach adopted following the similarity of the effectiveness results. The results were shown to be robust to variation explored in the sensitivity analysis.
Authors' conclusions There is no significant difference in the clinical outcomes and the overall cost for the 3-month episode of care for patients treated with either enoxaparin or unfractionated heparin. Savings associated with lower incidence of hospital re-admissions and shorter duration of venous thromboembolism-related re-admissions offset additional acquisition costs for anticoagulant medication among patients treated with enoxaparin.
CRD COMMENTARY - Selection of comparators The reason and rationale for the choice of the comparator, unfractionated heparin, were clear. You, as a database user, should consider if the same applies to your own setting.
Validity of estimate of measure of benefit Given the randomised design of the international study, the validity of the effectiveness results seems to be assured. The patient groups were comparable in their baseline characteristics, except for a somewhat greater proportion of males in the enoxaparin group (58.7% versus 50%). As the effectiveness analysis showed similarity between the 3 groups, the authors carried out a cost-minimisation analysis.
Validity of estimate of costs Sufficient details of cost estimation were given and resource use and unit costs were presented separately. The authors appropriately point out that additional protocol-driven costs, brought about by the requirements of the trial, may have imposed additional costs on the enoxaparin groups that would not occur in actual practice. The cost analysis was conducted only in the US settings, so the results might not be generalisable to other countries.
Other issues Appropriate comparisons were made with other studies. Limitations of the study include: the 3-month period of observation which may not have fully captured the impact of anticoagulant therapy on resource use, and the third-party payer perspective adopted in the study. A societal perspective might have identified additional costs related to the lost productivity while undergoing treatment.
Implications of the study The results suggest that enoxaparin, administered once or twice daily, is as safe and effective as unfractionated heparin and leads to fewer re-admissions. Although enoxaparin is more expensive, overall there is no difference in the costs of care. Within a naturalistic setting, enoxaparin may be more cost-effective but this remains to be demonstrated.
Source of funding Sponsored by Aventis SA (formerly Rhone-Poulenc Rorer Pharmaceuticals Inc), Bridgewater, NJ, and Rhone-Poulenc Rorer SA, Antony, France. Funded in part by National Research Award F32 HS000124 from the Agency for Health Care Policy and Research, Rockville, Md, USA (Dr Yusen).
Bibliographic details de Lissovoy G, Yusen R D, Spiro T E, Krupski W C, Champion A H, Sorensen S V. Cost for inpatient care of venous thrombosis: a trial of enoxaparin vs standard heparin. Archives of Internal Medicine 2000; 160: 3160-3165 Indexing Status Subject indexing assigned by NLM MeSH Enoxaparin /economics /therapeutic use; Female; Fibrinolytic Agents /economics /therapeutic use; Health Care Costs; Heparin /economics /therapeutic use; Hospitalization /economics; Humans; Male; Middle Aged; Single-Blind Method; Venous Thrombosis /drug therapy /economics AccessionNumber 22000008347 Date bibliographic record published 30/06/2001 Date abstract record published 30/06/2001 |
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