Self-contained patient data in ORCA to cope with an evolving vocabulary.

Because of the benefits of standardization in healthcare data for research, decision support, and quality assessment, much research effort focuses on collection of structured patient data. Many strategies to obtain such data are based on controlled vocabularies to guide data entry in a far more flexible way than a fixed-form approach. Medical controlled vocabularies evolve, but change is difficult to reconcile with standardization. Retrieval of data, collected with different versions of vocabularies, is not straightforward and has consequences for patient care and research. There are several strategies to cope with these problems: keep each version, keep a record of changes, or conversion of previously collected data. Each of these strategies has pros and cons regarding storage consumption, performance during patient care, and research. The approach in ORCA (Open Record for Care) is based on self-contained patient data and combines the strengths of these strategies.