This deliverable reports the cohort onboarding and metadata collection undertaken by Work Package 4 during the first four years of EPND. It describes how collaboration with cohort owners and Work Package 1 expanded the EPND Catalogue and supported the development of federated dataset discovery.

The report records 108 onboarded cohorts, covering 277,328 participants across 14 disease areas. High-level metadata include study descriptions, institutions and contact points, participant numbers, disease groups, and the availability of biosamples and imaging data. More detailed descriptions were collected for 41 datasets and 35 biosample collections, including information on their characteristics, use conditions and related publications.

Interoperability with the AD Workbench made a further 77 datasets discoverable through the EPND Catalogue, bringing the reported total to 118 datasets. For 17 cohorts, Work Package 4 also collected more detailed use-condition information aligned with Digital Use Conditions and Common Conditions of use Elements (DUC-CCE) profiles. Tailored procedures were established to support more direct data or sample requests through the Hub.

The deliverable also documents Work Package 4’s contribution to the Federated Discovery Pilot described in D1.5. This included identifying useful metadata and aggregate-data fields and providing cohorts for testing. The resulting network covered five nodes and 78 cohort or dataset entries, using core metadata and pre-aggregated record-level information rather than direct searches of individual participant records.

The report identifies practical challenges in obtaining detailed metadata, including limited staff time, differences in data-sharing infrastructure, and legal or consent-related constraints. Support measures included personalised outreach, structured Excel templates, individual calls, manuals, demonstration videos and onboarding webinars.

These results exceeded the planned coverage of 60 cohorts for metadata discovery and 30 for the record-level discovery work. The deliverable provides both a quantitative account of catalogue development and practical lessons for extending participation.

For more information, find the full Deliverable report here.