Introduction:
Improved use of clinical data is expected with clinical information systems in healthcare. To exchange clinical data in regional electronic health records (EHR) and national registries for quality and research purposes, structured and standardized data is needed.
The aim of this study was to investigate the potentials and challenges by one-time collection of clinical data for documentation in EHR and registries for quality and research purposes in head and neck cancer.

Method:
Clinical documentation activities were analysed using semi-structured interviews. A "follow-up" visit was chosen for semantic analysis with comparison of clinical data in EHR and registry for quality and research purposes. Clinical data was identified, structured and standardized with a reference, SNOMED CT terminology for the purpose of comparing clinical data in EHR and registry.

Results:
In comparison of free text in EHR from four medical centres, an underlying and uniform structure was identified. Core information in EHR and registry was identified and compared. An exact match was found for 9 out of 19 terms from the registry. A similar match was found for detailed descriptions of common adverse events. Both EHR and registry had core information with no compared match.

Discussion:
The level of structure of clinical data can be adapted to clinical practise. Further development of SNOMED CT could enhance coverage of clinical data in head and neck cancer. New use of clinical data raises privacy concerns.

Conclusion:
One-time data collection reduced parallel documentation, enabled retrieval and display of clinical information and guided data entry. Challenges were found using a terminology to standardize data and balancing the use of high- or semi structured clinical data. In this study a method was demonstrated for one-time data collection for multiple purposes. Further studies investigating the impact of one-time data collection in clinical practice are needed.