Opioid use disorder Cascade of Care: defining a taxonomy for measurement.

Background: The opioid use disorder Cascade of care (OUD Cascade) is a public health framework used by federal/state/other agencies and researchers to facilitate monitoring and evaluating responses to the opioid epidemic, including surveillance and performance evaluation. As the use of the framework proliferates, there is an urgent need to standardize stage definitions to accurately monitor and improve patient outcomes and to align interpretation of findings across settings.Objectives: Define a taxonomy to uniformly apply the OUD Cascade to improve delivery of OUD services and better compare patient outcomes across settings and populations.Methods: We conducted a narrative review and synthesis focused on research and guidelines defining and measuring four key OUD Cascade stages: OUD identification, service engagement, medication initiation, and retention. Included articles come from peer-reviewed literature and define and/or operationalize OUD Cascade stages and associated measures across six characteristics based on an adaptation of the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist including: 1) settings, 2) specific population, 3) perspective, 4) time horizon, 5) assumptions, and 6) analytic method.Results: Our review (n = 27 articles) and synthesis provide an overview of how OUD Cascade definitions and framework designs have been variously applied. We found considerable heterogeneity in study approaches for all four OUD Cascade stages. We define a taxonomy to guide future research emphasizing standardized definitions to harmonize efforts across settings. In particular, we emphasize the need for clarity in defining criteria for sample construction (i.e. Identification), clear distinctions between receipt of care services generally (i.e. Engagement) from MOUD Initiation specifically, and Retention definitions that use a 30+ day gap in treatment to define discontinuation.Conclusion: Establishing a shared taxonomy for key terms specifying OUD Cascade stages will help the field advance, compare approaches and results across settings, and improve population-level patient outcomes.