Cost-effectiveness analysis of antiplatelet therapy in the prevention of recurrent stroke in the UK - Aspirin, dipyridamole and aspirin-dipyridamole

Objectives: To evaluate the cost effectiveness from a UK health and social services perspective of antiplatelet therapies tested in the Second Europea n Stroke Prevention Study (ESPS-2) in preventing recurrent stroke. To demon strate the value of modelling studies in this area. Design and setting: A decision-analytic model was developed to evaluate hea lth outcomes and associated costs. Sources of data for efficacy, adverse ev ents, background event risks, disability and mortality were ESPS-2, the Oxf ordshire Community Stroke Project and UR national statistics. Published nat ional unit costs were applied to clinician panel estimates of resource use for acute stroke, rehabilitation and long term care. Outcome measures were strokes or disabled life-years averted, and disability-free, stroke-free or quality-adjusted life-years gained. Patients and interventions: 30-day survivors of ischaemic stroke treated wi th low dose aspirin, modified-release dipyridamole; the coformulation of lo w dose aspirin plus modified-release dipyridamole, or no antiplatelet thera py. Main outcome measures and results: The model predicted that over 5 years th e coformulation prevented 29 more strokes than aspirin alone per 1000 patie nts, at an additional cost of pound 1900 per stroke averted (1996 values). Over 5 years, each antiplatelet therapy was cost saving compared with no th erapy. Results were sensitive to the cost of acute care, the cost of long t erm care of disabled stroke survivors, the effectiveness of therapy and the background risk of recurrent stroke. In sensitivity analyses, the cost eff ectiveness did not exceed pound 7000 per stroke averted or pound 11 000 per quality-adjusted life-year (QALY) gained, except when varying the effectiv eness parameter. Conclusions: Application of a decision-analytic model to the results of ESP S-2 indicated that first-line therapy with the coformulation of modified-re lease dipyridamole and low dose aspirin to patients with a previous ischaem ic stroke is likely to generate significant health benefits at modest extra costs to health and social services. The extra costs of treatment are bala nced by the savings in future costs of acute care and long term care of the disabled. Future economic evaluations in this area should pay particular a ttention to the cost perspective, the duration of analysis, the selection o f trials from which effectiveness data are derived, and the impact of the p ooling of outcome events with potentially different economic consequences.