i2b2 ontologies have a column c_totalnum that can store the total count of patients associated with every item in the ontology tree. This can be visualized in the i2b2 webclient to assist with query building (e.g., to find concepts that have many patients) or be used for data quality (to find areas where patient counts do not make sense). It is also used by the query builder to optimize queries. The ENACT network uses these counts for additional analytics across their network. We recommend you run these counts after each ETL.