associated medical/encounter data where diligent research has determined that mistakes were made with the identification of patients and to split off encounter records from patients that are blended into the single AHLTA record. Master Patient Indexing is a feature of the AHLTA Clinical Data Repository (CDR). Over 100 CHCS host systems, DEERS (Defense Enrollment Eligibility Reporting System), and AHLTA Theater (the version being used in Iraq and other areas) all contributed patients into the CDR when it was created from 25 month data pulls back in 2004. Each CHCS patient registration links into AHLTA, some link to existing patients, but others are newly created. Complexity with patient names and methods of identifying them with other demographics can lead to duplication, both in a local CHCS system and in the central AHLTA CDR. There is currently a DHIMS contract working on improving the processes and automating the routines to resolve duplicate patients and prevent their creation in future. References Health care software