Background: Clinical data is abundant, but meaningful reuse remains lacking. Semantic representation using SNOMED CT can improve research, public health, and quality of care. However, the lack of applied guidelines to industrialise the process hinders sustainability and reproducibility. This work describes a guide for semantic representation of data elements with SNOMED CT, addressing challenges encountered during its application. The representation of the institutional data warehouse started with the guidelines proposed by SNOMED International and other groups. However, the application at large scale of manual expert-driven representation led to the development of additional rules.

Results: An eight-rule step-by-step guide was developed iteratively through focus groups. Continuously refined by usage and growing coverage, they are tested in practice to ensure they achieve the desired outcome. All rules prioritize maintaining semantic accuracy, which is the main goal of our strategy. They are divided into four groups which apply to understanding the data correctly (Context), and to using SNOMED CT properly (Single concepts first, Approved post-coordination, Extending post-coordination).

Conclusions: This work provides a practical framework for semantic representation using SNOMED CT, enabling greater accuracy and consistency by promoting a common method. While addressing challenges of large-scale implementation, the guide supports the drive from data centric models to a semantic centric approach, leveraging interoperability and more effective reuse of clinical data.