Each of the 16 HSN health systems maintain integrated electronic health records (EHRs) as well as highly curated virtual data warehouses. With appropriate IRB oversight, health systems’ EHRs and virtual data warehouses are used as data sources for HSN studies. HSN pragmatic trials, such as the PROUD trial, are designed to evaluate interventions’ effectiveness in regular, everyday clinical practice. As part of this design, pragmatic trials can draw on patients’ EHRs for outcome data, which allows for these trials to be implemented without the necessity of direct primary data collection from patients. For example, in the PROUD trial, the number of patient days of opioid use disorder medication treatment documented in the EHR in each clinic in the two years post-randomization is the primary outcome measure.
HSN observational studies such as HEDIS AOD-IET Measure Performance (CTN-0072-OT) and the Prescription Opioid Registry (CTN-0084) rely on the highly curated virtual data warehouses that each of the 16 HSN sites maintains as a member of the Health Care Systems Research Network (HCSRN) or the VA's Corporate Data Warehouse that spans all 21 VA networks. Programmers at each site transform EHR and claims data elements from local data systems to a virtual data warehouse standardized set of variable definitions, names, and codes. The common structure allows programming code for HSN observational studies developed at one site to be used at other sites to extract and analyze each site’s data. This distributed data model offers an efficient means to conduct multisite studies, while protecting the identity of patients, providers, and health systems and allowing researchers to access data from larger, diverse populations than they would otherwise be able to access within their own institution.
