Challenges and Opportunities in Changing Data Structures of Clinical Document Archives from HL7-V2 to FHIR-Based Archive Solutions.

: In 2018, a major replacement of clinical applications took place at the University Hospital of Giessen. One key part was the clinical document archive containing a vast collection of clinical data from the last 30 years. The aim of this sub-project was to move all data to a new system without any loss, while maintaining all functionality and all communication interfaces. This project successively resulted in a complete paradigm change in document storage. While the legacy clinical data repository (LCDR) was designed according to HL7-V2 principles, the replacement resulted in an HL7-FHIR implementation. The aim of this work is to discuss the differences between both approaches, the obstacles that appeared during migration, but also the opportunities resulting from the new philosophy, especially as far as the impact on the use of scientific data is concerned.