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HL7 Glossary

HL7 Glossary

A comprehensive guide to the definitions of key titles and acronyms used by the HL7 community.


Accountable Care Organization
An Accountable Care Organization (ACO), according to the Centers for Medicare & Medicaid Services (CMS) “is an organization of health care providers that agrees to be accountable for the quality, cost, and overall care of Medicare beneficiaries who are enrolled in the traditional fee-for-service program who are assigned to it.” Under the health care reform legislation passed in March 2010, the Medicare program is authorized to contract with ACOs.

Access Point
Radio-based device that provides users of wireless devices with access to a local are network (LAN).

AHIC – American Health Information Community
Also known as “the Community” formed to help advance efforts to reach the president’s call for most Americans to have electronic health records by 2014. See 

AHIMA – American Health Information Management System
A community of professionals engaged in health information management, providing support to members and strengthening the industry and profession. See

AMIA – American Medical Informatics Association
The first professional group to issue guidelines for physician-patient email.

ANSI – American National Standards Institute
The U.S. standards organization that establishes procedures for the development and coordination of voluntary American National Standards.

This term refers to the structure of an information system and how its pieces communicate and work together. Also see client/server and tiered architecture.

Abstract Syntax
Describes the services that DICOM applications can render to each other; they encode SOPs supported on the communicating AEs.
Generally equivalent to a SOP class, the specification used to define the information to exchange in a message; does not represent a specific instance of the data object, but rather a class of similar data objects that have the same properties. Examples: MR image storage, CT image storage, MWL.

AE – Application Entity
Uniquely identifies a DICOM device or program. Typically labeled with numbers and uppercase characters only.
An end point of a DICOM information exchange, including the DICOM network or media interface software; that is, the software that sends or receives DICOM information objects or messages. A single device may have multiple application entities.

AET – Application Entity Title
The externally known name of an application entity, used to identify a DICOM application to other DICOM applications on the network.

A network communication channel set up between application entities; the DICOM network data exchange between SCU and SCP peers. Each network transfer begins with an association establishment — a DICOM handshake.
DICOM association rules define the low-level protocols for DICOM network connectivity to ensure that two communicating DICOM applications (AEs) are compatible and transfer data in a well-defined format and order.


A measure of how much information can be transmitted at once through a communication medium, such as a telephone line, fiber-optic cable, or radio frequency.


CCHIT – Certification Commission for Healthcare IT
CCHIT serves as the recognized US certification authority for electronic health records (EHR) and their networks. In September 2005, CCHIT was awarded a 3-year contract by the U.S. Department of Health and Human Services to develop and evaluate the certification criteria and inspection process for EHRs and the networks through which they interoperate. CCHIT serves one of the ONC-ATCB for electronic health record (EHR) certification. CCHIT was certified by the ONC on September 3, 2010 and is authorized to certify complete EHR and EHR modules  Visit the CCHIT website.

Conformance Checking
Conformance checking or gap analysis for HL7 messages is a logical process used to determine whether a message from one particular medical device or application is compatible to the selected HL7 standard messaging format, or a custom format adopted by another device or application.

C is an established programming language found in many operating systems, including UNIX. C++, a daughter program based on objects, is quickly becoming a favored programming language as object-oriented technology gains popularity.

CIS – Clinical Information System
An Electronic Health record that is a clinical repository of patient data. The term CIS is sometimes used interchangeably with EMR.
Typically covers:
Pathology and radiology order entry and results reporting; Medication prescribing, supply and administration; Clinical work lists; Problem lists; Clinical notes; Decision support.


DICOM – Digital Imaging and Communications in Medicine
DICOM is a common format for image storage. It allows for handling, storing, printing, and transmitting information in medical imaging. Visit DICOM website.

The Transport Layer Security (TLS) protocol provides a means of adding security to DICOM communication.

Data Mining
Analyzing information in a database using tools that look for trends or anomalies without knowledge of the data’s meaning. Mining a clinical database may produce new insights on outcomes, alternate treatments, or effects of treatment on different races and genders.

Data Fields
Appendix A, the data dictionary, provides an alphabetical listings of data elements, listings of recommended coded values, and a cross reference data elements to segments.

Data Dictionary 
Part 6 of the DICOM standard. This part contains a registry of the DICOM Data Elements which assigns a unique tag, a name, value characteristics, and semantics to each Data Element. Also included in this part is a Registry of DICOM Unique Identifiers (UID).

Data Element
A subunit of an information object as defined by a single entry in the DICOM Data Dictionary (PS 3.6). An encoded Information Object Definition (IOD) Attribute that is composed of, at minimum, 3 fields: a Data Element Tag, a Value Length (VL), and a Value Field. For some specific Transfer Syntaxes, a Data Element also contains a Value Representation (VR) field. The description of the Data Element can be found in PS 3.5. Each Data Element holds an Attribute of a real world object.

Private Data Elements – A Data Element defined by an application and is not in the Standard DICOM Data Dictionary (PS 3.6). Private Data Elements all have a Group Number that is odd.
Retired Data Element – A Data Element that is unsupported beginning with DICOM version 3.0. Implementation may continue to support Retired Data Element for the purpose of backwards compatibility with versions 1.0 and 2.0

Data Element Tag
The first part of any Data Element. This is a 32-bit value that identifies the Data Element. It is made up of 2 16-bit values. The first is the Group Number and the second is the Element Number. The DICOM specification uses the following notation for a Data Element Tag: (0010:0030). This example is for the Patients Birthday.

An Internet zone of authority, part of the address structure.


EDI – Electronic Data Interchange
EDI is a standard format for exchanging business data. The standard is developed by the Data Interchange Standards Association. An EDI message contains a string of data elements; each represents a singular fact, such as a price, product model number, and is separated by delimiter. The entire string is called a data segment. One or more data segments framed by a header and trailer form a transaction set, which is the EDI unit of transmission (equivalent to a message). A transaction set often consists of what would usually be contained in a typical business document or form. The parties who exchange EDI transmissions are referred to as trading partners.

EHR – Electronic Health Record
An electronic record of health-related information on an individual that conforms to nationally recognized interoperability standards and that can be created, managed, and consulted by authorized clinicians and staff across more than one health care organization. EHR records include patient demographics, progress notes, SOAP notes, problems, medications, vital signs, past medical history, immunizations, laboratory data and radiology reports.

EMR – Electronic Medical Record
EMR is a computer-based patient medical record. An EMR facilitates access of patient data by clinical staff at any given location; accurate and complete claims processing by insurance companies; building automated checks for drug and allergy interactions; clinical notes; prescriptions; scheduling; sending to and viewing by labs; The term has become expanded to include systems which keep track of other relevant medical information. The practice management system is the medical office functions which support and surround electronic medical record.

Electronic medication administration record.

Electronic medical record adoption model.

Electronic protected health information.

Electronic personal health record.

ELINCS – EHR-Lab Interoperability and Connectivity Standards
The ELINCS specification provides a profile that refines (or constrains) “standard” HL7 messages to moving lab results from reference labs to physician offices.

Translation of data into a code in order to keep the information secure from anyone but the intended recipient.


Federally qualified health center.

An HL7 field is a string of characters defined by one of the HL7 data types.

Filed Components
A field entry may also have discernable parts or components. For example, the patient’s name is recorded as last name, first name, and middle initial, each of which is a distinct entity separated by a component delimiter (sub-subfield in astm e1238-94).

Field Separator
The HL7 field separator separates two adjacent data fields within an HL7 segment. It also separates the segment ID from the first data field in the segment. The value that represents the field separator may be defined differently for each message. Whatever character is the fourth character of the MSH segment serves as the field separator for all segments in the message. Absent other considerations, it is recommended that all sending applications use “|” as the field separator. However, all receiving applications are required to accept whatever character is included in this position and use it to parse the message.

Formatted Text data type. This data type is derived from the string data type by allowing the addition of embedded formatting instructions. These instructions are limited to those that are intrinsic and independent of the circumstances under which the field is to be displayed, FT supports width-independent and device-independent text display.


Refers to a person who has financial responsibility for the payment of a patient account.

Device and conversion method between heterogeneous networks or systems.

Group Number
The first part of a Data Element Tag. It is a 16-bit value that identifies the Group that the Data Element falls in to. All Standard DICOM PS 3.6 Group Numbers are even. Odd group numbers are reserved for Private Data Elements and are defined by a specific application. Starting with DICOM 3.0 that Group Number has no significance and should not be considered to Group any Tags even though similar Tags continue to share the same Group Numbers. See also Repeating Group.


The Health Insurance Portability and Accountability Act (HIPAA) was enacted by the U.S. Congress in 1996. Title II of HIPAA, known as the Administrative Simplification (AS) provisions, requires the establishment of national standards for electronic health care transactions and national identifiers for providers, health insurance plans, and employers. This is intended to help people keep their information private, though in practice, it is normal for providers and health insurance plans to require the waiver of HIPAA rights as a condition of service.
The Administration Simplification provisions also address the security and privacyof health data. The standards are meant to improve the efficiency and effectiveness of the nation’s health care system by encouraging the widespread use of electronic data interchange in the U.S. health care system.

HL7 – Health Level Seven
HL7 is a Standards Developing Organization accredited by the American National Standards Institute (ANSI) to author consensus-based standards representing a board view from healthcare system stakeholders. HL7 has compiled a collection of message formats and related clinical standards that define an ideal presentation of clinical information, and together the standards provide a framework in which data may be exchanged. Visit the HL7 organization website or HL7Standards.comfor more HL7 information.

HL7 Batch Protocol
The HL7 Batch Protocol transmits a batch of HL7 messages using FHS, BHS, BTS, and FTS segments to delineate the batch.

HIS – Hospital Information System
HIS is the main system in a hospital used by most caregivers. Sends ADT broadcasts to all ancillary applications. The HIS is typically the patient administrative system and order entry system for a hospital.


The ability of software and hardware on multiple pieces of equipment made by different companies or manufacturers to communicate and work together.

ICD-9 is a classification used in the medical field that stands for International Classification of Diseases, 9th revision. This classification is predominately the standard classification of diseases, injuries, and cause of death for the purpose of health records. The World Health Organization (WHO) assigns, publishes, and uses the ICD to classify diseases and to track mortality rates based on death certificates and other vital health records. Medical conditions and diseases are translated into a single format with the use of ICD codes.

Interface Engine
An interface enginecan transform or map the data to the receiving application’s requirements while the message is in transit so that it can be accepted by the receiving application. The application interface is built with one-to-many concepts in mind. These import/export modules then are connected to an interface engine so that the mapping, routing, and monitoring are managed by this system.

IHE – Integrating the Healthcare Enterprise
IHE is an initiative by healthcare professionals and industry to improve the way computer systems in healthcare share information. Visit the IHE website.


A platform-independent, object-oriented programming language developed by Sun Microsystems and modeled on the programming language C++. Java applets– miniature applications designed to run within another program–now are popular features of Web sites.


LIS – Laboratory Information System
LIS is an information system that receives, processes, and stores information generated by a medical laboratory processes. LIS is often interfaced with HIS and EMR applications.


Meaningful Use
A term associated with The American Recovery and Reinvestment Act of 2009 (ARRA) that authorizes the Centers for Medicare & Medicaid Services (CMS) to provide reimbursement incentives for medical professionals and hospitals that become compliant in the use of certified electronic health record (EHR) technology. Professionals and hospitals that meet the criteria of “meaningful use” will begin receiving incentive payments in 2011 with a gradual decline in reimbursement amounts until the year 2015. By this date, providers are expected to have adopted and be actively utilizing a certified EHR in compliance with the “meaningful use” definition or be subject to financial penalties under Medicare.


ONC – Office of the National Coordinator for Health Information Technology
Located within the Office of the Secretary for the U.S. Department of Health and Human Services (HHS), the Office of the National Coordinator (ONC)coordinates nationwide efforts to support the adoption of health information technology and the promotion of health information exchange to improve health care. The ONC position was established in 2004 with an Executive Order and legislatively mandated in the Health Information Technology for Economic and Clinical Health Act (HITECH Act) of 2009.

Open source
Software in which the source code is available to users, who can read and modify the code.


PACS – Picture Archiving Communication System
PACS are devoted to the storage, retrieval, distribution, and presentation of images. The medical images are stored in an independent format, most commonly DICOM.

PHR – Personal Health Record
PHR, as defined in Defining Key Health Information Technology Terms(The National Alliance for Health Information Technology, April 28, 2008): An electronic record of health-related information on an individual that conforms to nationally recognized interoperability standards and that can be drawn from multiple sources while being managed, shared, and controlled by the individual.

PMS – Practice Management System
PMS applications facilitate the day-to-day operations of a medical practice. PMS software enables users to capture patient demographics, schedule appointments, maintain lists of insurance payers, perform billing tasks, and generate reports. It handles the administrative and financial matters for a practice.

Point-To-Point Interfaces
point-to-point interface is one in which the receiving vendor provides a specification on what data it can receive and in what format it needs to be in. The sending application then builds an interface to that specification for that application. It is a one-to-one relationship. For each application requiring an interface, there is a new request and point-to- point interface developed.

Patient Record Locator 
The electronic means by which patient files are located to assist patients and clinicians to find test results, medical history, prescription data, and other health information. A record locator would act as a secure health information search tool


RIS – Radiology Information System
RIS is the main application in an imaging center or radiology department. RIS is used by to store, manipulate and distribute patient radiological data and imagery. RIS are used for patient scheduling, tracking, and image tracking.

RHIO – Regional Health Information Organization
The terms “RHIO” and “Health Information Exchange” or “HIE” are often used interchangeably. RHIO (regional health information organization) is a group of organizations with a business stake in improving the quality, safety and efficiency of healthcare delivery. RHIOs are the building blocks of the proposed National Health Information Network (NHIN) initiative proposed by David Brailer, MD, and his team at the Office of the National Coordinator for Health Information Technology (ONCHIT). To build a national network of interoperable health records, the effort must first develop at the local and state levels. The concept of NHIN requires extensive collaboration by a diverse set of stake holders. The challenges are many to achieve success for a health information exchange or a RHIO.

__Regular expression – In computing, a regular expression provides a concise and flexible means to “match” (specify and recognize) strings of text, such as particular characters, words, or patterns of characters. Common abbreviations for “regular expression” include regex and regexp. It is widely used for TAG Morphing and define rules for DCMSYS DICOM ROUTER and DICOM AND HL7 interface engine.


SLA – Service Level Agreement
A contract between a service provider and a user that specifies the level of service expected during a contract term. Service level agreements determine how performance will be measured and, in the event of underperformance, how the penalties will be calculated and paid.

SSL – Secure Sockets Layer
The Secure Sockets Layer (SSL) is a commonly-used protocol for managing the security of a message transmission on the Internet. SSL has recently been succeeded by Transport Layer Security (TLS), which is based on SSL. SSL uses a program layer located between the Internet’s Hypertext Transfer Protocol (HTTP) and Transport Control Protocol (TCP) layers.


The use of telecommunications and information technology to deliver health services and transmit health information over distance.

A form of telemedicine that involves the electronic transmission of radiological images from one location to another for the purposes of interpretation and/or consultation. Users in different locations may simultaneously view images with greater access to secondary consultations and improved continuing education.

Tag morphing
“Tag morphing” is the ability to retrieve an image or study from the archive or other Dicom repository in a fashion
such that one or more of the DICOM elements (DICOM HEADERS) are created, deleted or
manipulated to provide new value(s) for the DICOM element(s) so as to make the retrieving, storing, sharing
DICOM data properly. Dicom Systems refers it as DICOM transformation

“Transformation” is the equivalent as “Tag morphing”

TCP/IP – Transmission Control Protocol/Internet Protocol
TCP/IP is a low-level communications protocol used to connect hosts on the Internet or a network. TCP/IP connections are established between clients and servers via sockets. TCP/IP is stream-oriented meaning it deposits bits in one end and they show up at the other end.


VNA – Vendor Neutral Archive
A software solution that acts as a middleware application between one or many clinical workflow applications, formerly known as PACS, and various storage platforms and IT strategies. VNA will support: one or many clinical viewing applications, a standards based environment, storage virtualization strategies, robust business continuity deployments and virtual environments. We can put a link to our VNA video here

VPN – Virtual Private Network
A network that uses public connections, such as the Internet, to link users but relies on encryption and other security measures to ensure that only authorized users can access the network.


Web Server
A networked computer that stores and transmits documents and other data to Web browsers via HTTP, an Internet data transfer protocol.

WVHIN – West Virginia Health Information Network
Governor Joe Manchin signed legislation creating the West Virginia Health Information Network (WVHIN) into law on March 22, 2006. Senate Bill 170 created WVHIN to promote the design, implementation, operation and maintenance of a fully interoperable statewide network to facilitate public and private use of health care information in the state. The WVHIN is under the oversight of the West Virginia Health Care Authority. The WVHIN will support a variety of electronic clinical transactions, including disease management, preventive medicine alerts, and prescription drug tracking. The WVHIN will be managed and operated by a 17-member Board of Directors representing the state’s medical schools, medical associations and other health care providers.

Workgroup for electronic data exchange.


X12 provides for electronic exchange of business transactions-electronic data interchange (EDI). The American National Standards Institute (ANSI) chartered the Accredited Standards Committee (ASC) X12 to develop uniform standards.

XDM – Cross-enterprise Document Media Interchange
What it’s used for: According to IHE, XDM transfers documents and metadata using CDs, USB memory or email attachments. This profile supports environments with minimal capabilities in terms of using Web Services and generating detailed metadata. This standard is utilized by the Direct Project.

Extended address data type. In version 2.3, replaces the AD data type.

Extended composite ID number and name data type. In version 2.3, use instead of the CN datatype.

Extended composite name and ID number for organizations data type.

Extensible Markup Language. A WC3 standard, it is the universal format for structured documents and data on the web.

Extended person name data type. In version 2.3, replaces the PN data type.

Extended telecommunications number data type. In version 2.3, replaces the TN data type.


Z Segment
All message type and trigger event codes beginning with Z are reserved for locally defined messages. No such codes will be defined within the HL7 Standard.