Data Auditing and Quality Assurance in a Federated Learning Consortium; Getting the Best of Both Worlds from Cross-Institutional and In-House Data Quality Inspection

Introduction: Rare and heterogeneous disease research increasingly relies on privacy-enhancing technologies such as federated learning (FL) to enable cross-institutional collaboration across fragmented datasets. However, data quality assurance in FL can be limited, as individual-level data may not be directly accessible. While schema-dependent inspection offers a partial solution, it requires standardised schemas or resource-intensive frameworks, hindering scalability and collaboration. To address these challenges, we implemented two complementary dashboards and evaluated their interplay. Methodology: We adapted a recognised data quality control framework for re-use of electronic health record (EHR) data using breast cancer records from Centre Leon Berard into two dashboards: (1) an in-house dashboard for intra-clinic quality assessment, and (2) a federated dashboard for inter-clinic quality assessment. Artificial inconsistencies were introduced into distributed datasets mirroring the in-house source to evaluate detection capabilities. Results: The in-house dashboard provided granularity and reliability, pinpointing individual-level inconsistencies, while the federated dashboard enabled cross-institutional pattern detection - trade-offs inherent to their designs. The federated system revealed ecosystem-wide trends inaccessible to single-institution tools, whereas the in-house dashboard provided local validation and thoroughness. Discussion: Our findings confirm a complementary relationship: FL dashboards provide scalable, collaborative oversight but may require additional quality checks, while in-house tools ensure thoroughness at the cost of scalability. A combined model seemingly offers the optimal balance, accommodating both institution-specific needs and collaborative research requirements in evolving, multi-institutional ecosystems.