The Leeds Teaching Hospitals NHS Trust (LTHT) OMOP database is a robust, longitudinal dataset constructed using data from the electronic health records (EHR) of patients treated and diagnosed at Leeds Teaching Hospitals NHS Trust since 2003. This comprehensive resource is mapped to the OMOP CDM, ensuring interoperability with other OMOP databases, and enabling privacy-preserving, large-scale, multi-centre studies.

Encompassing a wide array of clinical data, the database includes information on demographics, diagnoses, procedures, medications and laboratory results. A particular strength lies in its detailed cancer-specific data, which supports in-depth analyses of treatment outcomes, survival rates, and disease progression. This makes it an invaluable resource for researchers focusing on oncology, as well as those interested in broader secondary care settings.

Researchers can draw insights from the LTHT OMOP database through federated analytics approaches as well as through the use of standardised OHDSI tools, which enable secure, privacy-preserving analyses across multiple institutions, eliminating the need to access individual-level patient data.

Notably, the LTHT OMOP database has been instrumental in several high-profile studies:

• HERON Network: LTHT is a member of the HERON network, funded by HDR UK, which focuses on enhancing the quality and impact of cancer research through federated analytics. LTHT participated in a study examining the use of antibiotics which are in the WHO watchlist for high risk of antimicrobial resistance. • DigiONE Pilot Studies: These studies analyse harmonised routine care data from OMOP databases in 6 digitally mature European hospitals. Three studies have been conducted to date, focusing on the impact of the COVID-19 pandemic on cancer care, on metastatic non-small cell lung cancer, and on HER2-/HR+ metastatic breast cancer. • FALCON-Lung Study: This study focused on the uptake of immune checkpoint inhibitors for metastatic non-small cell lung cancer across the world, and implemented a clinically validated line of therapy algorithm using systemic anti-cancer therapy data in the OMOP databases of 17 international institutions.

In summary, the LTHT OMOP database stands as a robust resource for secondary care research, particularly in oncology. Its comprehensive, high-quality data, combined with a commitment to national and international collaboration, positions it as a cornerstone for advancing healthcare research and improving patient outcomes.

The LTHT OMOP database consists of the following tables and data:

• Visit occurrence: includes inpatient and outpatient admissions for all patients that are or have been part of the cancer pathway, as well as all in-patient admissions for all other patients. The visit_detail table has not been populated. • Condition occurrence: populated with all diagnoses in the Trust since 2003. • Drug exposure: populated. Includes all anti-cancer drugs (chemotherapy and immunotherapy), and selected antibiotics medication (all antibiotics that are in the WHO watchlist for antimicrobial resistance, as well as access antibiotics). Plans to extend this to all medication prescribed. • Procedure occurrence: populated. Includes surgical and radiotherapy procedures delivered to patients with cancer, as well as all surgical procedures delivered to all other patients. • Measurement: populated with weight, height, TNM staging, performance status, and metastasis location data. • Observation: populated with ethnicity, IMD quintile, clinical trial participation (cancer only) and cancer histology data. • Device exposure: not populated. • Death: populated from ONS.