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Table 1 Assumptions made, how they were justified and their impact or weight in the model

From: Cost-effectiveness analysis of interventions for migraine in four low- and middle-income countries

  Assumption Justification Impact or weight in the model
1 Mild headache is not associated with disability This was a standard assumption [10,2] If the assumption were false, the cost-effectiveness of acute therapy would be slightly reduced
2 The pain associated with untreated migraine is at least moderate On the one hand, the diagnostic criteria for migraine describe the pain as at least moderate [11]; on the other hand, most clinical trials have recruited patients with at least moderate pain None
3 In a stepped-care treatment paradigm, triptans are used only by non-responders to simple analgesics This is the standard stepped-care paradigm, in which more expensive medications are reserved for those shown to need them The alternative would be a multiplicity of scenarios of no obvious interest
4 Acute treatment is initiated at attack onset (commencement of pain phase) The assumption was necessary to establish a time zero for purposes of effect calculation and was subject to further assumptions regarding patient adherence (see below) To the extent that the assumption was false, effect and therefore cost-effectiveness would be reduced
5 Each acute medication is used once per attack The assumption was necessary because of dependence on clinical trials data Additional doses would increase cost, particularly in the case of triptans (mean number of triptan doses per attack was reported as 1.4-1.5 in the USA [12], but this may not be representative of the countries of interest)
6 The endpoint of sustained headache-relief is an all-or-nothing response The assumption is in line with the standard definitions of pain relief and sustained pain freedom [13] The consequence of the assumption was an underestimation of effectiveness
7 Prophylaxis is offered only to the proportion of people with ≥3 migraine attacks/month As a recommendation based on frequency only, this was conservatively chosen [6] This is a clinical rather than an economic threshold, so it would be of limited interest to vary it. Lowering the threshold to ≥2 would increase the use of prophylactics with less gain per user
8 ASA has high current coverage (80%) in all study contexts except Zambia (50%) This was conservative; ASA is available almost universally, but not easily in rural Zambia No impact on cost-effectiveness estimations. Higher coverage would allow greater population health gain
9 As a result of non-adherence, a proportion of patients use OTC-drugs later than is ideal, and in suboptimal doses (described in the text). Best estimate, formed from our clinical judgement Better adherence would lead to higher health gain and therefore improve cost-effectiveness
10 Provider adherence is 75% Best estimate, based on our experience Higher adherence would allow greater population health gain, which would improve cost-effectiveness estimations
11 Public education improves adherence by 50% of the current deficit Based on what can be in expected in real world settings A greater improvement of consumer adherence would lead to improved cost-effectiveness as well as greater population health gain
12 Three-monthly doctor visits, each of 10 minutes’ duration, are needed for monitoring and prescription of triptans and prophylactics Reflects typical clinical need and treatment practice in these countries More or longer visits would increase costs
13 For consumer education, the number of leaflets needed is 50% of the disease prevalence, and one poster is required per 2,000 of the population Leaflet numbers allows for high circulation/exposure; poster numbers conform to WHO programme costing standards Increasing or decreasing leaflet or poster numbers would have a negligible impact on base-line results because the base-line cost of consumer education is very low (US$ 0.01-0.02 per capita)
14 For provider education, one physician per primary health-care centre per year will be trained for one day This represents an effective approach to reaching primary health care throughout the country Increasing or decreasing the number of trained providers would have a negligible impact on base-line results because the base-line cost of provider education is very low (US$ 0.01-0.02 per capita)