|
Cost-effectiveness of preference-based antithrombotic therapy for patients with nonvalvular atrial fibrillation |
Gage B F, Cardinalli A B, Owens D K |
|
|
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 Antithrombotic therapy for patients with nonvalvular atrial fibrillation.
Study population Hypothetical 65-year old patients with nonvalvular atrial fibrillation. The base case consisted of a hypothetical cohort whose members had no contraindication to antithrombotic therapy, would participate in their treatment decision making, and would be compliant with their therapy.
Setting Hospital setting. The study was carried out in the USA.
Dates to which data relate Effectiveness data were obtained from studies published between 1982 and 1998. Resource use data were retrieved from studies published between 1980 and 1995. The price year was 1994.
Source of effectiveness data Effectiveness data were derived from a review of previously published studies.
Modelling A decision-analytic Markov model was used to project final benefits and costs over a 10-year time horizon.
Outcomes assessed in the review Main baseline variables included rate of stroke, proportion of ischemic strokes, stroke risk reduction with prophylaxis, rate of major haemorrhage, proportion of major haemorrhage, and relative risk of non-stroke, non-haemorrhage death.
Study designs and other criteria for inclusion in the review 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 Number of primary studies included Approximately 18 studies were included.
Methods of combining primary studies Investigation of differences between primary studies Results of the review The rate of stroke without therapy was 5.3 for high risk patients, 3.6 for medium risk patients, and 1.6 for low risk patients. Stroke risk reduction with prophylaxis was 68% for warfarin and 22% for aspirin. The rate of major haemorrhage was 1.4% for warfarin and 0.9% for aspirin. The relative risk of death from atrial fibrillation was 1.3 and from atrial fibrillation and prior stroke was 2.3.
Measure of benefits used in the economic analysis The benefit measure was quality adjusted life years (QALYs), using a Markov model. Preferences were elicited from patients admitted to the Veterans Affairs Palo Alto Health Care System and at Stanford University, California, USA. Results from 69 patients who had atrial fibrillation, were at least 50 years of age, and could read English, were used. Utilities were measured with the time-trade-off method and implemented with the utility-assessment tool U-titer.
Direct costs All future costs were discounted at a rate of 5% per annum. Quantities and costs were not reported separately. The direct costs included the costs of prophylactic therapy, adverse events, and preference elicitation. The quantity/cost boundary adopted was that of the hospital. The estimation of quantities and costs was based on previously published studies and a telephone survey. The price year was 1994.
Statistical analysis of costs Sensitivity analysis In the sensitivity analysis, preference-based therapy was compared with aspirin for all therapy. The authors also examined how error in preference elicitation would affect quality-adjusted survival and costs, and how the patients' ability to comprehend and complete the preference assessment affected the success of preference-based therapy. The results were applied to patients aged 75 years, and costs of preference elicitation were varied. Finally, the effect of a third option, no anti-thrombotic therapy, was considered.
Estimated benefits used in the economic analysis For low-risk patients, the preference-based strategy and the warfarin strategy generated 6.75 and 6.70 QALYs, respectively. For medium-risk patients, the preference-based strategy and the warfarin strategy generated 6.62 and 6.60 QALYs, respectively. For high-risk patients, the preference-based strategy and the warfarin strategy generated 6.52 and 6.51 QALYs, respectively.
Cost results For low-risk patients, the costs of the preference-based strategy and warfarin strategy were $8,330 and $9,000, respectively. For medium-risk patients, the respective costs of each strategy were $10,770 and $10,860, and for high-risk patients they were $12,600 and $12,490.
Synthesis of costs and benefits Cost and benefit measures were not combined into a cost-utility ratio. The intervention was dominant for patients with AF and not more than one additional risk factor because it was associated with increased benefits and lower costs.
Authors' conclusions Preference-based treatment should improve quality-adjusted survival and reduce medical expenditure in patients who have nonvalvular atrial fibrillation and not more than one additional risk factor for stroke.
CRD COMMENTARY - Selection of comparators The rationale for the choice of the comparator was clear. Validity of estimate of measure of effectiveness The authors acknowledged that the benefits of incorporating patient preferences may be different in other populations. The efficacy of warfarin therapy relative to that of aspirin is uncertain for low-risk patients. If the advantage of warfarin over aspirin is greater than the authors assumed, then the benefit of preference-based therapy in low-risk patients would have been over-estimated. The authors only considered variability in preferences for strokes and for stroke prophylaxis. The inclusion of preferences for other events, such as gastrointestinal haemorrhage, could have increased the benefits of preference-based strategy. The authors did not examine how patients' preferences change over time. Validity of estimate of costs Only direct costs were included. The sensitivity analysis only varied the costs of preference elicitation. Other issues More details about the literature review could have been provided. The main issue left unanswered by the study is the generalisability of the effectiveness and cost results to a particular setting, country or population. Implications of the study A prospective trial comparing the two approaches on various populations would be of value in extending the present findings. Source of funding Supported by grants from the Palo Alto Institute for Research and Education and from the Veterans Affairs HSR&D Field Program. Dr Owens is supported by a Career Development Award from the Veterans Affairs Health Services Research and Development Service.
Bibliographic details Gage B F, Cardinalli A B, Owens D K. Cost-effectiveness of preference-based antithrombotic therapy for patients with nonvalvular atrial fibrillation. Stroke 1998; 29(6): 1083-1091 Other publications of related interest 1. Eckman M H, Levine H J, Pauker S G. Making decisions about antithrombotic therapy in heart disease: decision analytic and cost-effectiveness issues. Chest 1995;108(4 Supplement S):S457-S470.
2. Howard P A, Duncan P W. Primary stroke prevention in nonvalvular atrial fibrillation: implementing the clinical trial findings. Annals of Pharmacotherapy 1997;31(10):1187-1196.
3. Gage B F, Cardinalli A B, Albers G W, Owens D K. Cost-effectiveness of warfarin and aspirin for prophylaxis of stroke in patients with nonvalvular atrial fibrillation. JAMA 1995;274:1839-1845.
Indexing Status Subject indexing assigned by NLM MeSH Aged; Anticoagulants /administration & Aspirin /administration & Atrial Fibrillation /complications /drug therapy /psychology; Cerebrovascular Disorders /etiology /mortality /prevention & Cohort Studies; Cost-Benefit Analysis; Decision Trees; Embolism /complications; Female; Health Care Costs; Humans; Male; Middle Aged; Patient Satisfaction; Platelet Aggregation Inhibitors /administration & Quality-Adjusted Life Years; Risk Factors; Sensitivity and Specificity; Thrombolytic Therapy /economics; Warfarin /administration & control; dosage; dosage; dosage; dosage AccessionNumber 21998000853 Date bibliographic record published 30/09/1999 Date abstract record published 30/09/1999 |
|
|
|