A comparison of clinical trial and model-based cost estimates in glaucoma – The case of repeat laser trabeculoplasty In Ontario

Abstract

Economic evaluations of glaucoma interventions require accurate costs in addition to effectiveness data. However, the impact of different costing methods on cost estimates has not been investigated. Direct cost estimates alongside clinical trials may be labour-intensive and expensive, modelled cost using literature sources and institutional experience may be an alternative. We investigated modeled and directly collected costs of a trial comparing argon-and selective-laser trabeculoplasty (ALT and SLT) among glaucoma patients at St. Joseph's Health Care in London, ON between 2013 and 2014, also comparing ministry and societal perspectives and cost drivers. Model and trial cost estimates differed minimally for the ministry perspective (8% and 4% for ALT and SLT) despite differences in modeled and observed parameter values and treatment pathways. Labour accounted for 90% of total cost. Costs were similar for the societal perspective although there was sensitivity to assumptions regarding patient time loss. Indirect costs were at least as large as direct medical costs. Modeled costs were an acceptable substitute for directly measured costs in this scenario.