Intracranial Hemorrhage Following Anticoagulant Treatment in Denmark: Spontaneous Adverse Drug Reaction Reports Versus Real-World Data.

INTRODUCTION: In Denmark, physicians are legally obliged to report serious adverse drug reactions (ADRs), such as intracranial hemorrhage (ICH) following anticoagulant (AC) treatment, to the Danish Medicines Agency. We were therefore puzzled to discover a high number of reports concerning ICHs following treatment with the direct oral anticoagulants (DOACs) dabigatran, rivaroxaban, and apixaban compared with warfarin. This was surprising, as all DOACs have been found to be associated with a lower risk of ICH compared with warfarin in phase III randomized controlled trials. OBJECTIVES: The primary aim of the study was to estimate the level of underreporting of ICH as an ADR following treatment with warfarin, dabigatran, rivaroxaban, and apixaban. METHODS: This observational study covered a 5-year period (2014-2018). Using nationwide registries held by the Danish Health Data Authority, the number of users, exposure time in person-years, and related ICH events for each of the study drugs were estimated. Data on ADR-ICH reports were extracted from the interactive ADR overviews held by the Danish Medicines Agency. RESULTS: From 2014 to 2018, 97.0% of the identified warfarin-related ICH events were not reported as ADRs. For the DOACs, the level of underreporting ranged from 88.8 to 90.8%. CONCLUSION: We found a heavy and differentiated level of underreporting of ICH as an ADR following treatment with the four study drugs.

Mapping Outcomes and Registries Used in Current Danish Pharmacoepidemiological Research.

Purpose: There is an increasing need for national and international pharmacoepidemiological studies based on high-quality real-world data of which the Danish registries are a valuable source. In lack of a complete overview of which data are used to assess real-world drug safety and effectiveness outcomes, we aimed to map the outcomes, data sources, and the reporting of outcome quality in recent pharmacoepidemiological studies. Methods: We conducted a systematic mapping review of pharmacoepidemiological studies based on Danish registries investigating drug safety and/or effectiveness, published in the period 2018-2019, identified in PubMed and Scopus. Extraction included: Anatomical Therapeutic Chemical level 2 code for drug exposures, outcomes, outcome data sources, and quality of outcomes. Results: Of the 210 included studies, 96% used outcomes categorized as Clinical, 4% utilized outcomes categorized as Society-related, 5% used outcomes categorized as Healthcare cost and utilization, and 3% of the studies applied outcomes categorized as Patient-reported in which the percentages are not mutually exclusive. Diagnosis (66%) and Mortality (38%) were the two most utilized subcategories among those categorized as Clinical outcomes. Danish Health Data Authority and Statistics Denmark registries were the most reported outcome data sources (90%). Ninety-six studies (46%) reported one or more quality parameters related to their outcomes of interest with accuracy/validity being the most reported parameter (22%). Conclusion: The Danish registries support a wide range of outcomes. Across therapeutic areas, most studies investigate traditional clinical outcomes of disease and mortality based on data from a small number of available registries. In contrast, clinical and biochemical databases, despite potentially offering outcomes with high responsiveness, and the high-quality social and healthcare cost registries were rarely used as outcome data sources.