Evidence-based Medicine Toolkit

Appraising economic evaluations 67Does this economic evaluation provide a validcomparison of alternatives?5 Did the study identify all of the relevant costs for eachintervention?You should be satisfied that the study identified all the relevantcosts of delivering the interventions and providing care for theiroutcomes and valued them credibly. Costs will usually be brokendown into two parts:1 The unit cost for each element of an intervention (e.g. cost perGP consultation, cost per hospital day, cost per dose of a drug);and2 The resource use, that is, how many of units of each elementwere used in the study.The total cost is the unit cost multiplied by the resource use.It’s important to note that, in comparing different interventions,the analysis should show the costs avoided by providing an interventionthat prevents outcomes.You should consider whether all of the relevant cost elementshave been included. For example, costs may be restricted to directcosts associate with the intervention (drugs, staff costs in deliveringcare, costs of providing facilities), and may ignore indirectcosts such as lost economic productivity, travel costs incurred bypatients, etc.Incremental costs and benefitsEconomic evaluations are interested in the additional benefits tobe gained, and costs incurred, from one intervention as comparedto another. This is known as the incremental benefits and costs.6 Were costs identified prospectively?Some (deterministic) costs can be predicted in advance, whileother (stochastic) costs cannot and may vary from one patient toanother or from one setting to another. For these reasons, it’s bestif the evaluation compiles its cost information prospectively duringthe course of the study rather than retrospectively.