HL7 Health Information Exchange Standard (Health Level 7)

The standardized health information transmission protocol is a protocol for electronic transmission between different applications in the medical field. HL7 brings together standard formats used by different vendors to design interfaces between application software. It will allow various medical institutions to exchange data between heterogeneous systems.

The main application field of HL7 is HIS/RIS, which mainly regulates the communication between HIS/RIS systems and their equipment. It involves ward and patient information management, laboratory systems, pharmacy systems, radiology systems, Charging system and other aspects. The purpose of HL7 is to develop and develop hospital data information transmission protocols and standards, standardize clinical medicine and management information formats, reduce the cost of interconnection of hospital information systems, and improve the degree of data information sharing between hospital information systems.

The "Level 7" in Health Level 7 refers to the seventh layer, the highest layer in the OSI seven-layer model. But this does not mean that it follows the defined data elements of OSI layer seven, it is just used to form its own abstract data types and encoding rules. It also does not specify how to support data from OSI layers 1 to 6.

HL7 does not provide a complete "plug and play" solution, because there are two important influencing factors in the transmission environment of medical institutions:

⑴The transmission environment of medical institutions There is a lack of processing consistency in the transmission environment;

⑵The results generated need to be negotiated between users and manufacturers.

Therefore, it provides a flexible system that can select data and processing processes within a wide range, and includes as much as possible all known programs (Triggers) and data (Segments and Field) requirements.

In the HL7 communication protocol, message (Message) is the basic unit of data exchange. HL7 messages are automatically generated, which automatically converts HL7 standard documents into an HL7 rule database and part of the program data structure code. The specific work of implementing a communication standard is to generate a data structure and implement a constructor (Builder) and a parser (Parser). The data structure represents the interrelationship of various data objects in the standard. The constructor converts the data in the data structure into a data string that can be transmitted over an electronic data exchange medium. The parser can parse the data string back to the original data structure. The HL7 standard is a text-structured document. First, use some word processing tools to extract each data definition in the document into a data structure, and then store the structure in the predefined HL7 rule database. Then, develop a code generator that automatically generates a certain computer language code based on the contents of the rule database. Finally, these codes can be added to the program framework of the actual application.

Figure 1 illustrates the use of HL7 standards to interconnect various medical devices. ADT refers to admission, discharge and transfer, usually referred to as ADT (Ad-mission, Discharge, Transfer). ADT is mainly about the generation and update of patient personal information, as well as the exchange of information data such as patient visits. ADT is the most widely used aspect of the HL7 standard since any device that joins the medical system network requires the patient's personal information. Usually, the data entering an ADT system always has to be passed to various systems in the hospital, and in 2013 it even had to be passed to the insurance company. HL7 (Health Level 7), as an organization, was established in 1987. Since 1994, it has been one of the standards development organizations (SDO) authorized by the American National Standards Institute (ANSI). It is engaged in the research and development of medical service information transmission protocols and standards. non-profit organization.

HL7 currently has more than 2,200 members, including more than 1,500 group members, representing 90% of the world's major countries and information system suppliers, including medical. In addition to the United States, countries and regions participating in HL7 technical cooperation and promotion include Australia, Canada, China, Finland, Germany, Japan, the Netherlands, New Zealand, the United Kingdom, India, Argentina, South Africa, Sweden, South Korea, Taiwan, etc.

The purpose of the HL7 committee is to develop and develop hospital data information transmission protocols and standards, and optimize clinical and management data information procedures.

The HL7 committee (as of December 2002) has established 21 technical committees

Technical guidance, building a traceability system, Clinical Context Object Working Group (CCOW), clinical diagnosis support, Control, inquiry, education, financial management, international membership admissions, marketing, medical records, information management, modeling and methodology, physician orders, observation data, patient management, patient care, personnel management, process improvement, publishing, clinical research information Management, work organization and logistics, structured documentation, terminology.

15 Special Interest Groups (SIGs):

Arden Grammar, Attachments, Clinical Guidelines, Clinical Genetics, Social Basic Health Services, Compatibility, Electronic Medical Records (EMR), Government Programs, Image Integration, Java, Lab Automation and Testing, Drug Therapy, Safety and Liability, Templates, XML.

HL7 committees are not fixed, especially SIGs, which can be freely applied for and established by members. As a standard, HL7 is the seventh layer (application layer) protocol of the Open Systems Interconnection (OSI) seven-layer protocol.

It is a standard that regulates the transmission of medical data between various medical institutions, medical institutions and patients, medical administrative units, insurance units and other units.

As an information exchange standard, HL7 has released v2.0 v2.1 v2.2 v2.3 v2.3.1 since the release of V1.0 in 1987, and v2.4 in 2000. The v3.0 version has been developed using XML, but the HL7 v2.4 version is still the officially released version by ANSI.

HL7 goals

⑴ The HL7 standard should support data exchange under various technical environments, and should also support various programming languages ??and operating systems, as well as various communication environments.

⑵ Supports both single data stream and multi-data stream communication methods.

⑶ To maximize compatibility, special tables, encoding definitions, and message segments (such as HL7's Z-segments) are reserved for use by different users.

⑷ The standard must be extensible to support new requirements, including the expansion of the protocol itself and compatibility with existing systems and new systems.

⑸ The standard should be a widely accepted industrial standard based on full reference to existing product communication protocols.

⑹ The long-term goal of HL7 is to develop a standard or protocol for electronic data exchange in medical institutions. Layer 7 is the highest level of the International Standards Organization's (ISO) Open Systems Interconnection (OSI) model. This is not to say that HL7 is completely consistent with the OSI layer 7 principles defined by ISO. Furthermore, HL7 does not specify a set of ISO-approved specifications to occupy layers 1-6 of the HL7 abstract message specification role. But HL7 conforms to this conceptual definition of application-side to application-side interfaces located within Layer 7 of the OSI model.

In the OSI conceptual model, the functions of communication software and hardware are divided into layer 7. The HL7 standard mainly focuses on problems that occur at layer 7 or at the application layer. These are the definitions of the data exchanged between applications, the time of exchange, and application-specific errors in inter-application communication. However, protocols related to the lower layers of the OSI model are sometimes mentioned to help the system understand the context of the standard, which is necessary. They are also sometimes mentioned to help implementers build systems that work with HL7.

The HL7 Working Group is made up of volunteers who work on their own time or at the initiative of their employer. The membership of the HL7 working group has been, and will continue to be, open to those interested in building, developing, and refining Layer 7 interface standards for healthcare system network technologies.

This standard can address interfaces between different systems that can send or receive information including: patient admission/registration, discharge or transfer (ADT) data, queries, patients resources and schedules, physician orders, diagnostic results, clinical observations, fees, master file updates, medical records, arrangements, patient treatment arrangements, and patient care. This is not an attempt to assume a particular architecture related to the placement of data within the application, but is designed to support a central patient care system, as well as to support a distributed environment of data within departmental systems.

If we consider that most healthcare information system applications are the same as the various environments in which care is delivered, then it is clear that there are many interfaces that could benefit from such standardized definitions. Members involved in the process of writing the standards have high priority on the selection of interfaces. The purpose of HL7 is to prepare a complete standard for these interfaces, based on a general architecture that can strongly support many other interfaces. This standard has been put into use and serves as the basis for extending existing interface definitions and adding others.

This document is organized as follows. The remainder of this chapter includes: the basic rationale for developing the standard, the development goals of the standard, the scope of the working group affiliation, and a method for getting started. Hopefully this will help readers understand the basis for the decision to develop this standard.

The following chapters will respectively explain:

a) The entire structure of all interfaces (including the general query interface)

b) The admission, discharge, transfer and registration of patients

c) Physician order entry

d) Patient accounting (accounting) system

e) Clinical observation data, such as laboratory results, are sent as identifiable data elements ( instead of displaying directional text)

f) A common interface for synchronized public *** reference files (master files)

g) Medical information management

h) Patient and resource scheduling

i) Referral messages regarding patient transfers between the two facilities

j) Patient care messages to support problem-oriented communication , providing functional integrity for the implementation of clinical pathways in the computer information system - basic medical orders, financial, and inspection information are standardized and detailed, such as the patient's dietary taboos, religious beliefs, etc. according to the corresponding ISO standard description.

Achievability - Choose OSI layer 7 as the standard to ensure its achievability.

Compatibility and scalability - including support for traditional Chinese medicine measurement units.

Security - Due to the development and compatibility of HL7, security is difficult to ensure. Although digital signatures are supported, it mainly depends on the underlying network protocol. 1. Adopt point-to-point communication method to achieve docking of different systems;

2. Adopt HL7 server method. HL7 Server is actually an application server, forming a central database that resides in the HL7 interface, which can reduce the number of interfaces. , improve system reliability.