Proposed guidance on cost-avoidance studies in pharmacy practice.

PURPOSE Cost-avoidance studies of pharmacist interventions are common and often the first type of study conducted by investigators to quantify the economic impact of clinical pharmacy services. The purpose of this primer is to provide guidance for conducting cost-avoidance studies pertaining to clinical pharmacy practice. SUMMARY Cost-avoidance studies represent a paradigm conceptually different from traditional pharmacoeconomic analysis. A cost-avoidance study reports on cost savings from a given intervention, where the savings is estimated based on a counterfactual scenario. Investigators need to determine what specifically would have happened to the patient if the intervention did not occur. This assessment can be fundamentally flawed, depending on underlying assumptions regarding the pharmacists' action and the patient trajectory. It requires careful identification of the potential consequence of nonaction, as well as probability and cost assessment. Given the uncertainty of assumptions, sensitivity analyses should be performed. A step-by-step methodology, formula for calculations, and best practice guidance is provided. CONCLUSIONS Cost-avoidance studies focused on pharmacist interventions should be considered low-level evidence. These studies are acceptable to provide pilot data for the planning of future clinical trials. The guidance provided in this article should be followed to improve the quality and validity of such investigations.