International Validation of the Danish Vascular Registry Karbase: A Vascunet Report

Objectives: Vascunet has previously published an international comparison of registry data within vascular surgery. Data validity and completeness in participating registries is essential for a meaningful interpretation of differences between countries. The Vascunet collaboration has therefore developed a methodology for validation of international vascular registry data, previously used for validation of two national registries. This study aimed to assess the internal and external validity of the Danish vascular registry, Karbase, by independent Vascunet validators. Methods: Three of seven hospitals performing vascular surgery, covering 51% of carotid operations and 78% of abdominal aortic aneurysm (AAA) repairs in Denmark in 2016, were visited by two international validators. Independent evaluation was performed of carotid endarterectomy and AAA repair. Local administrative data were compared with Karbase registry data. External validation compared the numbers of cases in these two systems of data collection. Internal validation compared data accuracy and completeness with individual patient records. Results: Hospital administrative data identified 227/231 carotid and 522/576 abdominal aortic aneurysm (AAA) procedures, whereas Karbase identified 230/231 carotid and 567/576 AAAs. External validity was 99.6% for carotids and 98.4% for AAAs. In internal validation, 1.0% of variables were missing in hospital data whereas 1.7% were missing in Karbase. Data contained within the data fields of Karbase and hospital data were the same in 95.2% (95% CI 91.6-98.8%) for carotids and 97.4% (95% CI 95.4-98.8%) for AAAs. Conclusions: This study used the Vascunet template for international validation of registry data and demonstrated that Karbase is a reliable system of quality data collection for Danish vascular surgery, especially regarding endpoints. Data quality in the Karbase registry was clearly superior to local administrative data.