|Economic evaluation of oral sumatriptan compared with oral caffeine/ergotamine for migraine
|Evans K W, Boan J A, Evans J L, Shuaib A
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.
Oral drug therapy for migraine headache, specifically sumatriptan and caffeine/ergotamine.
Economic study type
Cost-effectiveness, cost-utility and cost-benefit analyses were performed.
The study population was stated to be individuals aged 18-65 years, with moderate to severe migraine. Pregnant women and refractory cases were not included.
The setting of the efficacy studies was primary care, the economic evaluation was carried out in Saskatchewan, Canada.
Dates to which data relate
Costs reported are in 1995 Canadian dollars. The earnings data were from 1991 and were converted to 1995. The efficacy studies were published from 1991-1995.
Source of effectiveness data
The evidence for effectiveness was based on a synthesis of randomized clinical trials.
A decision tree model was used to estimate the costs and utilities of the various therapy options.
Outcomes assessed in the review
The conversion of a moderate or severe headache to mild or no headache at 2 hours.
Study designs and other criteria for inclusion in the review
Only randomized, controlled clinical trials were included. No other inclusion/exclusion criteria were stated.
Sources searched to identify primary studies
MEDLINE, Embase, Scisearch, HealthPlan, IPA, Toxline, PsycInfo, and IMSworld R&D Focus were searched.
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
12 studies were included.
Methods of combining primary studies
Not stated, no weighting performed.
Investigation of differences between primary studies
Results of the review
The probability of achieving the primary outcome measure with sumatriptan was 55.8% The probability of achieving the primary outcome measure with caffeine/ergotamine was 37.9% The risk of recurrence within 48 hours was 40.6% for sumatriptan, and 29.7% for caffeine/ergotamine
Measure of benefits used in the economic analysis
The measures of benefit were: migraine avoided, Quality Adjusted Life Years, net economic benefit. Decision tree modelling was used to calculate expected costs. The human capital approach was used for the cost-benefit analysis. Utilities were assigned using the Quality of Well Being Scale. The probability of individual symptoms occurring was then based on a consensus of the authors, and an epidemiologic study in the literature.
Costs were not discounted. Costs and quantities were not reported separately. Drug costs, hospitalization costs, physician costs and the cost of lost earning by the patient were measured. Both the societal and health department perspective were studied. Estimation of expected costs was derived from the decision tree model. The sources of cost data were as follows:
(1) Outpatient drug prices were obtained from a random survey of 20 community pharmacies. The lowest price quoted for each drug was used.
(2) Hospital drugs and supplies: a non-random survey of wholesalers and hospitals.
(3) Other hospital costs: Statistics Annual Canada Hospital Returns.
(4) Physician costs: provincial fee schedule via telephone survey.
All costs were converted to 1995 Canadian dollars. Prescription dispensing fees were excluded because they were assumed to be the same in both groups.
Indirect costs were not discounted. Costs and quantities were not reported separately. The incremental productive output was calculated. These values applied to patients only. The estimation of quantities was based on epidemiologic study data from 1992. The estimation of average earnings was based on 1991 Canada census data indexed to 1995.
Both simple and probabilistic (Monte Carlo simulation) sensitivity analyses were carried out, to test the robustness of conclusions. The variables analyzed were: drug costs, hospital and emergency department costs, utilities, effectiveness of drugs, average earnings, migraine frequency.
Estimated benefits used in the economic analysis
Incremental Quality Adjusted Life Years afforded to patients taking sumatriptan, rather than caffeine/ergotamine for moderate or severe migraine = 0.22. It was assumed that 17.9% more attacks would be aborted when using sumatriptan rather than caffeine/ergotamine. Side effects of the two drug therapies were not considered.
The total cost of an episode of migraine was Can$22.56 for sumatriptan, and Can$4.71 for caffeine/ergotamine. Based on the assumptions used in the decision tree, the incremental cost of using sumatriptan rather than caffeine/ergotamine for moderate or severe migraine was Can$17.34 per episode.
Synthesis of costs and benefits
The benefit/cost data were reported in cost per attack aborted, cost per Quality Adjusted Life Year, and net benefit.
Incremental cost per attack aborted with Sumatriptan was -Can$25 from the societal perspective, and Can$98 from the health department perspective.
Incremental cost per QALY was -Can$7,507 from the societal perspective, and Can$29,366 from the health department perspective.
Net benefit was Can$42 per year, from the societal perspective.
From the health department perspective, the results are not sensitive to changes in any of the parameters tested. From the societal perspective, the results were found to be sensitive to changes in relative drug effectiveness. The net benefit would change from positive to negative if the difference in effectiveness between the two drugs is less than 11.2%. With the probabilistic sensitivity analysis, it was found that there was a 73% chance that the health benefits would be positive, and 74% that the net economic benefit would remain positive. There was less than 1% chance that health departments would have a net savings by using sumatriptan. Subgroup analysis based on severity of attack showed that on all three types of economic analysis, and from both the societal and health department perspectives, sumatriptan had a greater benefit in severe versus moderate attacks.
This economic evaluation showed that incremental health benefits were obtained from using oral sumatriptan rather than oral caffeine/ergotamine and that these benefits were achieved at moderately acceptable incremental costs to third party payers if past decisions on the adoption of other health technologies into general usage were used as a guide. When society as a whole was considered, rather than just the third party payer perspective, the health benefits also resulted in a net reduction of overall costs to society.
CRD COMMENTARY - Selection of comparators
The reason for the choice of comparators is clear, both being commonly used oral agents for migraine.
Validity of estimate of measure of effectiveness
The study is based on randomized, controlled, clinical trials. However, only one trial involving caffeine/ergotamine versus sumatriptan was found. While other studies using sumatriptan were identified to help in constructing the decision tree model, no other studies using caffeine/ergotamine were used. Thus, the probabilities relating to caffeine/ergotamine are less reliable. Inclusion of side effects would have provided a more complete analysis.
Validity of estimate of costs
The source of cost data is well described. The presentation of some costs are in aggregate form based on outcome, making generalizability difficult.
(1) the Friction Method for calculating indirect costs might have been preferred, as the human capital approach tends to over-estimate benefits.(2) The Quality of Well Being scale used to calculate utility, resulted in migraine having a utility that is 30% worse than being dead. This would tend to make the cost-utility analysis results less believable for most readers.
Implications of the study
Under the assumptions used, sumatriptan is a good first line agent for treating migraine. More research is needed with a controlled study in actual use.
Source of funding
Funded by the Canadian Coordinating Office for Health Technology Assessment (CCOHTA) - a publicly funded, independent organisation.
Evans K W, Boan J A, Evans J L, Shuaib A. Economic evaluation of oral sumatriptan compared with oral caffeine/ergotamine for migraine. PharmacoEconomics 1997; 12(5): 565-577
Subject indexing assigned by NLM
Administration, Oral; Caffeine /administration & Cost-Benefit Analysis; Ergotamine /administration & Migraine Disorders /drug therapy; Sensitivity and Specificity; Sumatriptan /administration & Vasoconstrictor Agents /therapeutic use; dosage; dosage; dosage /therapeutic use
Date bibliographic record published
Date abstract record published