A Master Patient Index (MPI) makes use of sophisticated algorithms to allow for patient identification and linking to a patient’s electronic medical record (EMR). It basically provides a link to the correct patient record in those organizations that utilize EMRs. An MPI’s accuracy can be attributed to its probabilistic matching techniques that use any available fields for matching, despite discrepancies in how various healthcare facilities track information.

An MPI is the cornerstone of any data-sharing initiative. Without a list, to say that a specific record is in the database, there is no way to know what patients are included. An EMR provides the clinical information about a patient, while the MPI is the index for that data. An MPI typically lists data points about a patient such as patient’s last name, first name, date of birth, gender, address, phone number, and dates and types of visits to the healthcare organization.

A Regional Health Information Organization (RHIO) or a National Health Information Network (NHIN) needs to have a MPI in order to locate and link to the correct patient record. They use MPIs to keep track of information kept in their data warehouse. The information listed in the MPI provides the ability for the institution to confirm that a particular patient is the correct person.

A RHIO or NHIN or community of hospitals that chooses to share data and utilize a MPI will have to work out a means of sharing and data standards, such as what information will be listed in the MPI. The Health Information Management Association (HIMA) has published rules of core MPI data elements.

An MPI can link a patient to the correct EMR in a case where there is no common denominator.

All providers will feed the MPI demographic information about patients, and the MPI will determine which patient information matches; then it can be queried to determine where records are located. An MPI is a very important piece of the solution, and its role is analogous between all three environments – a RHIO, a NHIN, and a community of hospitals. The MPI is the glue that ties all the information together.

A particularly critical role of an MPI is in the case of a patient who visits different hospital emergency rooms in an attempt to obtain narcotics prescriptions. ER providers will be notified of previous attempts when they enter the patient’s name into the computer upon check-in, if their MPI includes data such as previous visits and clinical problems, as many do.

MPIs can also help medical providers determine if they have the correct patient – in the case of a patient who may have checked in to her physician’s office as Jane Smith, into the laboratory as Jane E. Smith, and into the ER as J. E. Smith, all on various occasions over a period of time.

A healthcare organization has to have a strong baseline of patient information in the MPI in order to have an accurate EMR.

MPIs were one of the earliest patient safety initiatives, and have been around since the 1980s. Their usage increased as healthcare organizations merged and grew larger, and thus needed an efficacious method to match patient names with the correct data. The MPI, at source level, has been around for decades.

The MPI is the “key piece” for RHIOs and other data sharing networks, because it allows healthcare providers to access the correct patient information, which promotes data integrity. In the case of data sharing across a server or a network, if the MPI data is not clean and complete, then the data that is shared isn’t worthwhile, because there may be doubt about its accuracy.

According to AHIMA, an accurate MPI must include these core data elements: name, address, identifier, date of birth, gender, race, ethnicity, alias (if any), social security number, facility ID, account number, admission date, discharge date, encounter or service type, and patient disposition. Optional data elements are marital status, telephone number, mother’s maiden name, place of birth, advance directive and surrogate decision making, organ donor status, emergency contact, allergies/reactions, and problem list (master list of all patient’s health problems or diagnoses).

An Enterprise Master Patient Index (EMPI) takes the MPI one step further. It is a database that contains a unique identifier for every patient in the healthcare organization, such as the medical center, rehab facilities,  outpatient clinics and practice offices. An EMPI cross references patient identifiers across multiple information systems to identify each patient, perform global patient searches and matching, consolidate duplicate patient records, create complete views of patient information and share data across multiple facilities and information systems.

The St. Louis region, for example, is currently implementing a Network Master Patient Index (NMPI) health information exchange across the major safety net health care providers in St. Louis City and County. It is expected to improve patient care by enabling an exchange of clinical information; identifying Medicaid and uninsured patients without an identified primary care physician; enabling patient matching across member organizations while maintaining secure data; using a messaging system to enhance communication between physicians, care coordinators, primary care physicians/staff, and specialists; and providing an aggregation of individual patient admission/discharge/transfer information among the member organizations.