Opioid maintenance treatment in the Czech Republic, Norway and Denmark: a study protocol of a comparative registry linkage study.

Introduction: Opioid maintenance treatment (OMT) varies across settings and between countries. We plan to use data from several nationwide health and population registers to further improve the knowledge base established from earlier studies. Our aim is to study OMT adherence trajectories and to identify factors associated with improved outcomes for OMT patients across the Czech Republic, Norway and Denmark, in order to further improve OMT and our understanding of the key elements of treatment success.