KEY_NRD is a HCUP record identifier created specifically for the Nationwide Readmissions Database (NRD). Its purpose is to uniquely identify records so that the data elements from different NRD files can be combined. KEY_NRD does not link to other HCUP databases or to external databases.

KEY_NRD is a unique record identifier and cannot be used to track a person over time. The values of KEY_NRD differ from year to year, except across the 2013-2014 NRD. The values of KEY_NRD in 2013-2014 are similar.