Health data warehouse (HDW)
A health data warehouse (HDW; in French, entrepôt de données de santé, EDS) is a platform that collects, harmonises and stores health data from multiple source systems, such as electronic health records, laboratory and imaging systems, biobanks and administrative databases, to make it available for secondary use: research, innovation, quality improvement, health system management and, increasingly, training of AI models. University hospitals (for example the AP-HP warehouse in Paris), regional networks, national infrastructures and, in a growing number of cases, pharmaceutical and MedTech companies operate such platforms.
France has the most developed regulatory framework. Since 2021 the CNIL has published a reference framework (référentiel) for health data warehouses: a warehouse that conforms to it may be created on a declaration of conformity, otherwise a CNIL authorisation is required. The framework sets conditions on purposes (excluding, for example, commercial prospecting), data sources, patient information and objection rights, pseudonymisation, access governance through a scientific and ethics committee, security (including HDS certified hosting), retention (generally 20 years) and the requirement that each downstream study comply with MR-004 or obtain its own authorisation. Comparable frameworks exist in other countries (German university medicine data integration centres, Finnish Findata, Danish national registries), and the European Health Data Space will turn such warehouses into data holders supplying health data access bodies from 2029.
Building or using a warehouse raises the full range of GDPR questions: identifying the controller (hospital, consortium, industrial partner) and any joint controllers; the legal basis (public interest or legitimate interest with Art. 9(2)(j)); transparency towards patients who are not individually contacted; a mandatory DPIA; security and access measures; the status of data made available to users as pseudonymised or anonymised; and transfer rules where users or cloud providers are outside the EEA. iliomad supports hospitals and companies in creating warehouses and in accessing them; see health data warehouse services, the French HDW guideline and the HDW guide in the resource centre.
