HERC: Observational Medical Outcomes Partnership (OMOP)
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Observational Medical Outcomes Partnership (OMOP)


The Observational Medical Outcomes Partnership (OMOP) is a common data model that allows for comparison across disparate observational data sources. The idea is to transform data into a common model with similar data dictionaries to aid analysis. VA data in OMOP do not provide additional data, but rather pull from various sources across the VA Corporate Data Warehouse (CDW) to centralize VA data with a standard vocabulary. For more information on OMOP CDW data, see the VHA Data Portal (http://vaww.vhadataportal.med.va.gov/DataSources/OMOPCDWData.aspx; VA intranet only).

HERC has worked with the OMOP team to put VA cost data into the OMOP data model. The primary challenge with this transform is that the data in CDW that OMOP draws from may not be the same as the data used for VA accounting of costs.


OMOP access can be requested through DART for research projects or ePAS for operations use. See the VHA Data Portal for more information (http://vaww.vhadataportal.med.va.gov/DataSources/OMOPCDWData.aspx; VA intranet only).

Inpatient Costs in OMOP

VA considers inpatient stays to be any visits in which a patient stays overnight in a facility, including post-acute care, nursing facility care, and domiciliary services. This includes episodes where a patient moves between these types of care. Outside VA, inpatient stays are generally considered separate from long-term care. To work around this, Managerial Cost Accounting (MCA) inpatient treating specialty (TRT) tables are used. These tables are broken into months, allowing for matching on different types of inpatient care to match OMOP definitions. For stays with more than one type of inpatient care (e.g. acute care hospital and inpatient rehab) costs are distributed evenly over the full length of each type of stay. As an example, a patient that spent time in acute care and then went to post-acute care will have this stay to broken up into two episodes to satisfy OMOP logic. The total cost is then broken into a per-day cost and assigned accordingly. 

Outpatient Costs in OMOP

Similar to inpatient services, MCA data are used to populate OMOP cost data. Specifically, the MCA outpatient table (DSS.OUT) provides costs at the level of a visit to a specific stop code on a specific day for a specific patient. This allows researchers to link to other information in the OMOP tables that is associated with a visit at the patient-date-stop code level. 


VINCI's VA OMOP Academy includes resources for using VA OMOP data including training videos, common VA OMOP SQL examples, anda sandbox to practice SQL queries on de-identified data (VA intranet only: https://sps.vinci.med.va.gov/prod/vincipedia/VINCIPedia/OMOP%20Academy.aspx).


Last updated: April 23, 2023