A proposal for international collaboration through the VLFDC

Karen Woo

Based on a presentation given at the 2020 European Society for Vascular Surgery (ESVS) annual meeting (ESVS Month; 29 September–29 October, virtual), Karen Woo, Christian Behrendt, and Peter Lawrence detail a proposal for international collaboration in the study of rare vascular diseases through the Vascular Low Frequency Disease Consortium (VLFDC).

The VLFDC is a model for investigating uncommon vascular diseases.1 In managing uncommon vascular diseases, providers frequently only have the guidance of case reports, small case series, and occasionally meta-analyses where the data is collected differently at each institution. Thus, the objective of the VLFDC is to retrospectively compile standardised multi-institutional data to examine all facets of uncommon vascular diseases.

The VLFDC accepts project proposals on a quarterly basis and proposals can be submitted by anyone. The proposals are reviewed by the steering committee that includes representatives from the various geographic regions of the USA as well as Canada, Europe, Asia, and South America.

The first step in developing a successful VLFDC proposal is a comprehensive literature review. If the literature review demonstrates that there are inconsistent treatment recommendations, lack of evidence and/or small reported sample sizes regarding the proposed disease topic, this suggests that the topic is appropriate for the VLFDC. Next, the study protocol is developed, including specific aims, hypotheses, inclusion/exclusion criteria, suggested diagnosis and procedure codes to identify patients, background, sample size calculation, and analytic plan. A disease-specific database is constructed and data dictionary is created which clearly defines each data point and response option. Once the investigators are satisfied that the protocol and database have been optimised, US and international contributors are invited to participate in the multi-institutional stage of the study. Examples of required documentation can be found at: http://surgery.ucla.edu/vlfdc.

Data entry is performed using a web-based survey mechanism. The data dictionary is provided so that the data entered is standardized to the study definitions. All data is de-identified with no patient identifiers to include dates of service. All dates are measured in days/months/years from a designated “time zero” such as the date of diagnosis or the date of surgery. In the USA, and most other countries, sharing of this type of data between institutions is acceptable with approval from local institutional review boards or the equivalent. However, in the European Union (EU), sharing of de-identified institutional data is not acceptable and can be subject to large monetary fines, making it difficult for collaborators in EU countries to participate in the VLFDC.

One approach to address this situation is to have a collaborator within the EU who serves to collect and aggregate the EU data for each VLFDC study. The VLFDC would then send the aggregated US and other international data to the EU collaborator, together with analytic code for the required analyses. The EU collaborator would subsequently aggregate all of the US, EU and international data and analyze it using the analytic code and transmit the results back to the VLFDC. While this approach introduces an additional step in the process and requires an EU collaborator who is willing, liable and available to serve as the EU point of contact, this coordination between VLFDC and the EU would prove extremely valuable.

For each VLFDC study, all contributors who participated in the data collection and fulfill the standards of the journal become authors on the manuscript(s). Typically, the VLFDC aims to present the study abstract at a national US meeting such as the Vascular Annual Meeting or the Society for Clinical Vascular Surgery Annual Meeting. The VLFDC also aims to publish studies in the Journal of Vascular Surgery. For studies that have significant contribution from EU partners, joint presentation at a US and a European meeting, as well as joint publication in the Journal of Vascular Surgery and the European Journal of Vascular and Endovascular Surgery can be considered. While this would require some coordination, it can certainly be achieved and would provide value for all participants and bolster the international collaboration.

International collaboration enables learning about the incidence and management of vascular diseases in other geographic regions and cultures. We have learned that while carotid body tumours are low frequency in most regions, they are common in the high altitude areas of South America. We have also learned from Asia that most spontaneous mesenteric dissections resolve without intervention. These lessons improve our overall understanding of vascular disease. The VLFDC looks forward to collaborating with our international colleagues and is certain that an acceptable solution to the EU data collection issue can be achieved.


  1. Larence PF, Baril DT, Woo K. Investigating uncommon vascular diseases using the Vascular Low Frequency Disease Consortium. J Vasc Surg 2020; 72:1005–10.

Karen Woo is an associate professor of surgery at UCLA, Los Angeles, USA.

Christian Behrendt works at the Department of Vascular Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.

Peter F Lawrence is a vascular surgeon and professor of vascular surgery in Los Angeles, USA.

The authors have no disclosures.


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