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Economic evaluation of outpatient treatment with low-molecular-weight heparin for proximal vein thrombosis |
O'Brien B, Levine M, Willan A, Goeree R, Haley S, Blackhouse G, Gent M |
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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 Outpatient treatment with low-molecular-weight heparin (LMWH) for proximal vein thrombosis.
Economic study type Cost-effectiveness analysis.
Study population Patients with symptomatic acute proximal deep vein thrombosis treated as outpatients.
Setting Hospital and community. The economic study was carried out in Canada.
Dates to which data relate Effectiveness and resource use data corresponded to patients enrolled in a randomized trial the results of which were published in 1996. The price year was 1997.
Source of effectiveness data The evidence for final outcomes was derived from a single study.
Link between effectiveness and cost data The costing was prospectively performed on one stratum of the patient sample used in the effectiveness study.
Study sample Power calculations were not reported as being used to determine the sample size. 300 patients who presented as outpatients were assigned treatment with either LMWH primarily at home, or continuous intravenous standard heparin in the hospital. 151 were randomized to receive standard heparin in the hospital and 149 to receive low-molecular-weight heparin at home. 157 patients, who were admitted at night or over a weekend, and 43 patients who were hospitalised for other reasons such as surgery, and in whom DVT was subsequently diagnosed (but who were included in the original clinical trial) were excluded from the economic evaluation.
Study design The study was a multi-centre randomized controlled trial (RCT). The time frames for the study were a heparin treatment period of approximately 7 to 10 days following randomization and the warfarin treatment period of 3 months. Loss to follow-up was not reported. In the original clinical trial consisting of 500 patients, randomization was stratified according to the 3 groups of patient presentation: outpatients; those admitted at night or during the weekend; and patients who were already in the hospital.
Analysis of effectiveness The basis (intention to treat or treatment completers only) for the effectiveness analysis was not explicitly specified. The primary outcome used in the effectiveness analysis was the incidence of clinical events, specifically symptomatic recurrent venous thromboembolism within 90 days after randomization and bleeding during the period of administration of study medication (or within 48 hours after its discontinuation). Health-related quality of life was quantified at baseline prior to randomization and at day 7 for both treatment groups, using the Medical Outcomes Study Short-Form 36. 138 patients in the standard heparin group and 137 patients in the LMWH group completed the questionnaire at baseline, and 123 standard heparin patients and 125 LMWH patients completed the questionnaire at day 7.
Effectiveness results There were 59 suspected clinical events among the 151 patients randomized to standard heparin, compared with 56 events among the 149 patients receiving low-molecular-weight heparin, a difference that was not statistically significant (p=0.88). There was no significant difference in the number of confirmed thromboembolic events or bleeds between the two patient groups; 11 thromboembolic events and 1 bleed in the standard heparin group, and 10 thromboembolic events and 4 bleeds in the LMWH group. The change in scores from baseline to day 7 was not significantly different between the treatment groups for 7 of the 8 domains; the one exception being the domain of social functioning, where a greater improvement was observed for the low-molecular-weight heparin group than the for standard heparin group (p=.005).
Clinical conclusions There is no statistically significant difference in safety or efficacy between the two treatment groups. Health-related quality of life associated with outpatient treatment is at least as good, and may be better in some domains such as social functioning, than hospital-based heparin treatment.
Measure of benefits used in the economic analysis No summary benefit measure was identified in the economic analysis, and only separate clinical outcomes were reported. As a result, the study may be regarded as a cost-consequences analysis.
Direct costs Discounting was not applied due to the short period of the study (less than 1 year). Quantities and costs were analysed separately. The primary viewpoint of the analysis was societal, including costs to the health care system, and travel costs for patients. Direct costs were classified as scheduled treatment costs (including LMWH and standard heparin, hospital days, clinic visits, routine monitoring tests, and nurse home visits), non-scheduled investigation and treatment costs (including hospital admissions, days on intensive care unit, days on ward, outpatient visits, and diagnostic investigations), and patient travel. Study nurses recorded resources used by patients in both groups prospectively on case report forms. A committee adjudicated as to whether contacts with the health care system were likely to be related to the disease or its management. The committee was blind to treatment assignment and had predefined criteria with which to determine whether events were related to the study. Acquisition costs of standard heparin and warfarin were obtained from two hospital pharmacies in Hamilton, Ontario. Relevant price weights for hospital resources were estimated using data from a fully allocated, patient-level, itemised costing known as the Ontario Case Costing Project. The cost of physician services was evaluated using appropriate fees from the Ontario Health Insurance Plan Schedule of Benefits. The cost of nurse home visits was based on average cost per visit from home care programmes in the Toronto, Ontario area. For the heparin period only, patients reported kilometres travelled associated with therapy to permit calculation of travel costs. Travel cost was estimated at the McMaster University reimbursement rate of Can$0.35 per kilometre. 1997 price data were used. The costs of warfarin during the warfarin-only period were excluded because this was common to both treatment groups.
Statistical analysis of costs Costs were compared using nonparametric statistical methods because of skewed distributions. 95% confidence intervals (CIs) for the differences between the groups in mean cost were computed using bootstrap methods. The Wilcoxon rank sum test was used to test hypotheses.
Indirect Costs Discounting was not applied due to the short period of the study (less than 1 year). Quantities and costs were analysed separately. The perspective adopted in the cost analysis was that of society. For the combined heparin and warfarin treatment periods, days lost from work by patients or caregivers were recorded in order to estimate productivity losses. The cost of work absence was evaluated using the industrial average wage rate for Ontario. The date to which the price data referred was 1997.
Currency Canadian dollars (Can$). A conversion rate of Can$1= US$0.7 was reported.
Sensitivity analysis One-way and two-way sensitivity analyses were conducted in order to explore the robustness of the analysis to alternative price weights and to provide a range of price weights for hospital stay and drug acquisition which would facilitate generalisation to clinical practice in the United States.
Estimated benefits used in the economic analysis The reader is referred to the measure of benefit and effectiveness sections of this abstract.
Cost results Mean scheduled costs for standard heparin were Can$3,514 versus Can$897 for LMWH. There was, therefore, a cost saving in scheduled treatment costs associated with low-molecular-weight heparin of Can$2,617 per patient (95% CI: Can$2,311 - 2,964; p<0.001).
With respect to nonscheduled investigations and treatment costs, there was a significant trend toward a higher cost of Can$85 per patient receiving low-molecular-weight heparin (Can$937 versus Can$852 for standard heparin, 95% CI: Can$ -597 - 840) (p=0.62).
Patient costs and lost productivity were significantly lower for the low-molecular-weight heparin group by Can$513 per patient (Can$957 for standard heparin versus Can$444 for LMWH, 95% CI: Can$ -1,122 - Can$-71) (p=0.02).
The total cost per patient randomized to standard heparin was Can$5,323 versus Can$2,278 for the low-molecular-weight heparin: a societal cost saving per patient using low-molecular-weight heparin of Can$3,045 (95% CI: Can$2,012 - Can$4,050; p<0.001).
Synthesis of costs and benefits Synthesis was not undertaken since the use of LMWH at home was a dominant strategy (equal efficacy with lower costs) compared to the use of standard heparin. The robustness of the cost savings was established in the sensitivity analyses.
Authors' conclusions For patients with acute proximal vein thrombosis, treatment at home with low-molecular-weight heparin is less costly than hospital-based treatment with standard heparin. The economic evidence in favour of outpatient treatment with low-molecular-weight heparin exhibits dominance; a situation of reduced cost is created with no compromise in clinical outcomes or patients' quality of life.
CRD COMMENTARY - Selection of comparators A justification was given for the choice of the comparator (the use of hospital-based treatment with standard heparin). It was regarded as the standard treatment in the context in question. You, as a database user, should consider whether this is a widely used health technology in your own setting.
Validity of estimate of measure of benefit The internal validity of the effectiveness results is likely due to the use of a randomized design. The study may be regarded as a cost-consequences analysis.
Validity of estimate of costs Resource quantities were reported separately from prices and adequate details of the methods of quantity and cost estimation were given.
Other issues The authors' conclusion was justified given the use of a randomized design and the sensitivity analysis performed. The issue of generalisability to other settings or countries was addressed and appropriate comparisons were made with other studies.
Implications of the study The economic attractiveness of home-based treatment with low-molecular-weight heparin has already led to its adoption by Kaiser Permanente, a large health maintenance organization in southern California.
Source of funding Funded in part by a grant from Rhone-Poulenc Rover, Montreal Quebec (Dr O'Brien). Dr O'Brien is also supported by a career award in health sciences from the Medical Research Council of Canada and the Prescription Drug Manufacturers' Association of Canada, Ottawa, Ontario.
Bibliographic details O'Brien B, Levine M, Willan A, Goeree R, Haley S, Blackhouse G, Gent M. Economic evaluation of outpatient treatment with low-molecular-weight heparin for proximal vein thrombosis. Archives of Internal Medicine 1999; 159: 2298-2304 Other publications of related interest Levine M, Gent M, Hirsch J et al. A comparison of low molecular weight heparin administered primarily at home with unfractionated heparin administered in the hospital for proximal deep vein thrombosis. New England Journal of Medicine 1996;334:677-681.
Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Anticoagulants /economics /therapeutic use; Canada; Cost-Benefit Analysis; Female; Heparin, Low-Molecular-Weight /economics /therapeutic use; Humans; Male; Middle Aged; Prospective Studies; Venous Thrombosis /drug therapy /economics AccessionNumber 21999008322 Date bibliographic record published 31/07/2000 Date abstract record published 31/07/2000 |
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