Programmatic Theme: Clinical Research Informatics

Reliable cohort discovery is an essential early part of clinical study design. Indeed, it is the defining feature of many clinical research networks, including the recently launched Accrual to Clinical Trials (ACT) network. As currently deployed, however, the ACT network only allows cohort queries in isolated silos, rendering cohort discovery across sites unreliable. Here we demonstrate a novel protocol to provide network participants access to more accurate combined cohort estimates (union cardinality) with other sites. A two-party Elgamal protocol is implemented to ensure privacy and security imperatives, and a special attribute of Bloom filters is exploited for accurate and fast cardinality estimates. To emulate mandatory privacy protecting obfuscation factors (like those applied to the counts reported for individual sites by ACT), we configure the Bloom filter based on the individual site cohort sizes, striking an appropriate balance between accuracy and privacy. Finally, we discuss additional approval and data governance steps required to incorporate our protocol in the current ACT infrastructure.

Learning Objective: 1. Limitations in current cohort discovery systems for cross-site clinical trials.
2. Key design and implementation requirements for multi-site joint cohort discovery.
3. How to design secure protocols to fulfil the above requirements.
4. Basic understanding of Elgamal cryptosystem, Homomorphic encryption and Boom filters.


Xiao Dong (Presenter)
University of Illinois at Chicago

David Randolph, University of Illinois at Chicago

Keywords, Themes & Types