Purpose: Linked health-care registries and high coverage in Nordic countries lend themselves well to epidemiologic research. Given its relatively high incidence in Western Europe, complexity in diagnosis, and challenges in registration, multiple myeloma (MM) wasselected to compare registries in Denmark, Finland, and Sweden.Patients and Methods: Data were obtained from four archetypal registries in each country (spanning January 2005–October 2018):National Patient Registry (NPR), Prescribed Drug Registry (PDR), Cancer Registry (CR), and Cause of Death Registry. Patients newlydiagnosed with MM who received MM-specific treatment were included. PDR/NPR treatment records were used to assess incidentNPR cases. The registration quality of MM-specific drugs in the PDR of each country was also evaluated.Results: In Denmark, only 6% of patients in the NPR were not registered in the CR; in Sweden, it was 16.9%. No systematicdifferences were identified that could explain this discrepancy. In Denmark, lenalidomide and bortezomib were registered in the NPRwith high coverage, but less expensive drugs typically given in combination with bortezomib were not covered in any of the registries.In Finland and Sweden, bortezomib records were not identified in the PDR, but some were in the NPR; other drugs had good coveragein the PDR.Conclusions: The registries evaluated in this study can be used to identify the MM population; however, given the gaps in MMregistration in the Finnish and Swedish CRs, Danish registries provide the most comprehensive datasets for research on treatmentpatterns for MM.
